diff --git a/benchmarks/encodedecode.js b/benchmarks/encodedecode.js
index 2a9efda..384b8c1 100644
--- a/benchmarks/encodedecode.js
+++ b/benchmarks/encodedecode.js
@@ -1,11 +1,9 @@
-var msgpack = require('../')()
-var msg = { hello: 'world' }
-var encode = msgpack.encode
-var decode = msgpack.decode
-var max = 100000
-var start
-var stop
-var i
+const msgpack = require('../')()
+const msg = { hello: 'world' }
+const encode = msgpack.encode
+const decode = msgpack.decode
+const max = 100000
+let i
 
 function run () {
   for (i = 0; i < max; i++) {
@@ -16,8 +14,8 @@ function run () {
 // preheat
 run()
 
-start = Date.now()
+const start = Date.now()
 run()
-stop = Date.now()
+const stop = Date.now()
 console.log('time', stop - start)
 console.log('decode/s', max / (stop - start) * 1000)
diff --git a/benchmarks/parseshortmap.js b/benchmarks/parseshortmap.js
index b49befb..d9fded4 100644
--- a/benchmarks/parseshortmap.js
+++ b/benchmarks/parseshortmap.js
@@ -1,11 +1,9 @@
-var msgpack = require('../')()
-var bl = require('bl')
-var msg = bl(msgpack.encode({ hello: 'world' }))
-var decode = msgpack.decode
-var max = 1000000
-var start
-var stop
-var i
+const msgpack = require('../')()
+const bl = require('bl')
+const msg = bl(msgpack.encode({ hello: 'world' }))
+const decode = msgpack.decode
+const max = 1000000
+let i
 
 function run () {
   for (i = 0; i < max; i++) {
@@ -16,8 +14,8 @@ function run () {
 // preheat
 run()
 
-start = Date.now()
+const start = Date.now()
 run()
-stop = Date.now()
+const stop = Date.now()
 console.log('time', stop - start)
 console.log('decode/s', max / (stop - start) * 1000)
diff --git a/example.js b/example.js
index dfb8d11..048d232 100644
--- a/example.js
+++ b/example.js
@@ -1,16 +1,16 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var msgpack = require('./')() // namespace our extensions
-var a = new MyType(2, 'a')
-var encode = msgpack.encode
-var decode = msgpack.decode
+const Buffer = require('safe-buffer').Buffer
+const msgpack = require('./')() // namespace our extensions
+const a = new MyType(2, 'a')
+const encode = msgpack.encode
+const decode = msgpack.decode
 
 msgpack.register(0x42, MyType, mytipeEncode, mytipeDecode)
 
-console.log(encode({ 'hello': 'world' }).toString('hex'))
+console.log(encode({ hello: 'world' }).toString('hex'))
 // 81a568656c6c6fa5776f726c64
-console.log(decode(encode({ 'hello': 'world' })))
+console.log(decode(encode({ hello: 'world' })))
 // { hello: 'world' }
 console.log(encode(a).toString('hex'))
 // d5426161
@@ -25,14 +25,14 @@ function MyType (size, value) {
 }
 
 function mytipeEncode (obj) {
-  var buf = Buffer.allocUnsafe(obj.size)
+  const buf = Buffer.allocUnsafe(obj.size)
   buf.fill(obj.value)
   return buf
 }
 
 function mytipeDecode (data) {
-  var result = new MyType(data.length, data.toString('utf8', 0, 1))
-  var i
+  const result = new MyType(data.length, data.toString('utf8', 0, 1))
+  let i
 
   for (i = 0; i < data.length; i++) {
     if (data.readUInt8(0) != data.readUInt8(i)) { // eslint-disable-line
diff --git a/index.js b/index.js
index 6557e35..b12620d 100644
--- a/index.js
+++ b/index.js
@@ -1,17 +1,17 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var assert = require('assert')
-var bl = require('bl')
-var streams = require('./lib/streams')
-var buildDecode = require('./lib/decoder')
-var buildEncode = require('./lib/encoder')
-var IncompleteBufferError = require('./lib/helpers.js').IncompleteBufferError
-var DateCodec = require('./lib/codecs/DateCodec')
+const Buffer = require('safe-buffer').Buffer
+const assert = require('assert')
+const bl = require('bl')
+const streams = require('./lib/streams')
+const buildDecode = require('./lib/decoder')
+const buildEncode = require('./lib/encoder')
+const IncompleteBufferError = require('./lib/helpers.js').IncompleteBufferError
+const DateCodec = require('./lib/codecs/DateCodec')
 
 function msgpack (options) {
-  var encodingTypes = []
-  var decodingTypes = new Map()
+  const encodingTypes = []
+  const decodingTypes = new Map()
 
   options = options || {
     forceFloat64: false,
@@ -56,8 +56,8 @@ function msgpack (options) {
     }
 
     function reEncode (obj) {
-      var buf = bl()
-      var header = Buffer.allocUnsafe(1)
+      const buf = bl()
+      const header = Buffer.allocUnsafe(1)
 
       header.writeInt8(type, 0)
 
diff --git a/lib/codecs/DateCodec.js b/lib/codecs/DateCodec.js
index 2c92fda..a073d7c 100644
--- a/lib/codecs/DateCodec.js
+++ b/lib/codecs/DateCodec.js
@@ -5,9 +5,9 @@ function encode (dt) {
     return
   }
 
-  var millis = dt * 1
-  var seconds = Math.floor(millis / 1000)
-  var nanos = (millis - seconds * 1000) * 1e6
+  const millis = dt * 1
+  const seconds = Math.floor(millis / 1000)
+  const nanos = (millis - seconds * 1000) * 1e6
 
   if (seconds < 0 || seconds > 0x400000000) {
     // Timestamp96
@@ -16,7 +16,7 @@ function encode (dt) {
 
     encoded.writeUInt32BE(nanos, 1)
 
-    var hex = ''
+    let hex = ''
     if (seconds >= 0) {
       const padhex = '0000000000000000'
       hex = seconds.toString(16)
@@ -27,8 +27,8 @@ function encode (dt) {
       // reverse sign
       // keep all bits 0 and first 1 from right
       // reverse all other bits
-      var bin = (seconds * -1).toString(2)
-      var i = bin.length - 1
+      let bin = (seconds * -1).toString(2)
+      let i = bin.length - 1
       while (bin[i] === '0') {
         i--
       }
@@ -52,10 +52,10 @@ function encode (dt) {
     const encoded = Buffer.allocUnsafe(9)
     encoded[0] = -1
 
-    var upperNanos = nanos * 4
-    var upperSeconds = seconds / Math.pow(2, 32)
-    var upper = (upperNanos + upperSeconds) & 0xffffffff
-    var lower = seconds & 0xffffffff
+    const upperNanos = nanos * 4
+    const upperSeconds = seconds / Math.pow(2, 32)
+    const upper = (upperNanos + upperSeconds) & 0xffffffff
+    const lower = seconds & 0xffffffff
 
     encoded.writeInt32BE(upper, 1)
     encoded.writeInt32BE(lower, 5)
@@ -74,8 +74,11 @@ function check (obj) {
 }
 
 function decode (buf) {
-  var seconds
-  var nanoseconds = 0
+  let seconds
+  let nanoseconds = 0
+  let upper
+  let lower
+  let hex
 
   switch (buf.length) {
     case 4:
@@ -86,8 +89,8 @@ function decode (buf) {
     case 8:
       // Timestamp 64 stores the number of seconds and nanoseconds that have elapsed
       // since 1970-01-01 00:00:00 UTC in 32-bit unsigned integers, split 30/34 bits
-      var upper = buf.readUInt32BE(0)
-      var lower = buf.readUInt32BE(4)
+      upper = buf.readUInt32BE(0)
+      lower = buf.readUInt32BE(4)
       nanoseconds = upper / 4
       seconds = ((upper & 0x03) * Math.pow(2, 32)) + lower // If we use bitwise operators, we get truncated to 32bits
       break
@@ -97,11 +100,11 @@ function decode (buf) {
       // since 1970-01-01 00:00:00 UTC in 64-bit signed integer and 32-bit unsigned integer
 
       // get seconds in hex
-      var hex = buf.toString('hex', 4, 12)
+      hex = buf.toString('hex', 4, 12)
       // check if seconds is a negative number
       if (parseInt(buf.toString('hex', 4, 6), 16) & 0x80) {
         // convert to binary
-        var bin = ''
+        let bin = ''
         const pad8 = '00000000'
         hex.match(/.{1,2}/g).forEach(function (byte) {
           byte = parseInt(byte, 16).toString(2)
@@ -120,7 +123,7 @@ function decode (buf) {
       nanoseconds = buf.readUInt32BE(0)
   }
 
-  var millis = (seconds * 1000) + Math.round(nanoseconds / 1E6)
+  const millis = (seconds * 1000) + Math.round(nanoseconds / 1E6)
 
   return new Date(millis)
 }
diff --git a/lib/decoder.js b/lib/decoder.js
index d43d52c..a64130b 100644
--- a/lib/decoder.js
+++ b/lib/decoder.js
@@ -1,7 +1,7 @@
 'use strict'
 
-var bl = require('bl')
-var IncompleteBufferError = require('./helpers.js').IncompleteBufferError
+const bl = require('bl')
+const IncompleteBufferError = require('./helpers.js').IncompleteBufferError
 
 const SIZES = {
   0xc4: 2,
@@ -46,7 +46,7 @@ module.exports = function buildDecode (decodingTypes, options) {
       buf = bl().append(buf)
     }
 
-    var result = tryDecode(buf, 0)
+    const result = tryDecode(buf, 0)
     // Handle worst case ASAP and keep code flat
     if (!result) throw new IncompleteBufferError()
 
@@ -58,7 +58,7 @@ module.exports = function buildDecode (decodingTypes, options) {
     if (buf.length <= initialOffset) return null
 
     const bufLength = buf.length - initialOffset
-    var offset = initialOffset
+    let offset = initialOffset
 
     const first = buf.readUInt8(offset)
     offset += 1
@@ -112,7 +112,7 @@ module.exports = function buildDecode (decodingTypes, options) {
     if (inRange(0xcc, 0xcf)) return decodeUnsignedInt(buf, offset, size - 1)
     if (inRange(0xd0, 0xd3)) return decodeSigned(buf, offset, size - 1)
     if (inRange(0xd4, 0xd8)) {
-      var type = buf.readInt8(offset) // Signed
+      const type = buf.readInt8(offset) // Signed
       offset += 1
       return decodeExt(buf, offset, type, size - 2, 2)
     }
@@ -152,12 +152,12 @@ module.exports = function buildDecode (decodingTypes, options) {
   }
 
   function decodeArray (buf, initialOffset, length, headerLength) {
-    var offset = initialOffset
+    let offset = initialOffset
     const result = []
-    var i = 0
+    let i = 0
 
     while (i++ < length) {
-      var decodeResult = tryDecode(buf, offset)
+      const decodeResult = tryDecode(buf, offset)
       if (!decodeResult) return null
 
       result.push(decodeResult[0])
@@ -169,9 +169,9 @@ module.exports = function buildDecode (decodingTypes, options) {
   function decodeMap (buf, offset, length, headerLength, options) {
     const _temp = decodeArray(buf, offset, 2 * length, headerLength)
     if (!_temp) return null
-    const [ result, consumedBytes ] = _temp
+    const [result, consumedBytes] = _temp
 
-    var isPlainObject = !options.preferMap
+    let isPlainObject = !options.preferMap
 
     if (isPlainObject) {
       for (let i = 0; i < 2 * length; i += 2) {
@@ -216,22 +216,22 @@ module.exports = function buildDecode (decodingTypes, options) {
     var negate = (buf[offset] & 0x80) == 0x80; // eslint-disable-line
 
     if (negate) {
-      var carry = 1
-      for (var i = offset + 7; i >= offset; i--) {
-        var v = (buf[i] ^ 0xff) + carry
+      let carry = 1
+      for (let i = offset + 7; i >= offset; i--) {
+        const v = (buf[i] ^ 0xff) + carry
         buf[i] = v & 0xff
         carry = v >> 8
       }
     }
 
-    var hi = buf.readUInt32BE(offset + 0)
-    var lo = buf.readUInt32BE(offset + 4)
+    const hi = buf.readUInt32BE(offset + 0)
+    const lo = buf.readUInt32BE(offset + 4)
     return (hi * 4294967296 + lo) * (negate ? -1 : +1)
   }
 
   function decodeUnsignedInt (buf, offset, size) {
     const maxOffset = offset + size
-    var result = 0
+    let result = 0
     while (offset < maxOffset) { result += buf.readUInt8(offset++) * Math.pow(256, maxOffset - offset) }
     return [result, size + 1]
   }
@@ -243,7 +243,7 @@ module.exports = function buildDecode (decodingTypes, options) {
   }
 
   function decodeSigned (buf, offset, size) {
-    var result
+    let result
     if (size === 1) result = buf.readInt8(offset)
     if (size === 2) result = buf.readInt16BE(offset)
     if (size === 4) result = buf.readInt32BE(offset)
@@ -252,7 +252,7 @@ module.exports = function buildDecode (decodingTypes, options) {
   }
 
   function decodeFloat (buf, offset, size) {
-    var result
+    let result
     if (size === 4) result = buf.readFloatBE(offset)
     if (size === 8) result = buf.readDoubleBE(offset)
     return [result, size + 1]
@@ -264,7 +264,7 @@ module.exports = function buildDecode (decodingTypes, options) {
     const decode = decodingTypes.get(type)
     if (!decode) throw new Error('unable to find ext type ' + type)
 
-    var value = decode(toDecode)
+    const value = decode(toDecode)
     return [value, headerSize + size]
   }
 }
diff --git a/lib/encoder.js b/lib/encoder.js
index c812e5c..098b954 100644
--- a/lib/encoder.js
+++ b/lib/encoder.js
@@ -1,16 +1,16 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var bl = require('bl')
-var isFloat = require('./helpers.js').isFloat
+const Buffer = require('safe-buffer').Buffer
+const bl = require('bl')
+const isFloat = require('./helpers.js').isFloat
 
 module.exports = function buildEncode (encodingTypes, options) {
   function encode (obj) {
     if (obj === undefined) throw new Error('undefined is not encodable in msgpack!')
 
-    if (obj === null) return Buffer.from([ 0xc0 ])
-    if (obj === true) return Buffer.from([ 0xc3 ])
-    if (obj === false) return Buffer.from([ 0xc2 ])
+    if (obj === null) return Buffer.from([0xc0])
+    if (obj === true) return Buffer.from([0xc3])
+    if (obj === false) return Buffer.from([0xc2])
 
     if (obj instanceof Map) return encodeMap(obj, options, encode)
 
@@ -43,7 +43,7 @@ module.exports = function buildEncode (encodingTypes, options) {
 //
 
 function encodeArray (array, encode) {
-  const acc = [ getHeader(array.length, 0x90, 0xdc) ]
+  const acc = [getHeader(array.length, 0x90, 0xdc)]
 
   // This has to be forEach; Array.prototype.map preserves missing values and
   // Array.prototype.values yields them as undefined
@@ -59,8 +59,8 @@ function encodeArray (array, encode) {
 }
 
 function encodeMap (map, options, encode) {
-  const acc = [ getHeader(map.size, 0x80, 0xde) ]
-  const keys = [ ...map.keys() ]
+  const acc = [getHeader(map.size, 0x80, 0xde)]
+  const keys = [...map.keys()]
 
   if (!options.preferMap) {
     if (keys.every(item => typeof item === 'string')) {
@@ -75,17 +75,17 @@ function encodeMap (map, options, encode) {
 }
 
 function encodeObject (obj, options, encode) {
-  var keys = []
+  const keys = []
 
-  for (let key in obj) {
-    if (obj.hasOwnProperty(key) &&
+  for (const key in obj) {
+    if (Object.prototype.hasOwnProperty.call(obj, key) &&
         obj[key] !== undefined &&
         typeof obj[key] !== 'function') {
       keys.push(key)
     }
   }
 
-  const acc = [ getHeader(keys.length, 0x80, 0xde) ]
+  const acc = [getHeader(keys.length, 0x80, 0xde)]
 
   if (options.sortKeys) keys.sort()
 
@@ -97,22 +97,22 @@ function encodeObject (obj, options, encode) {
 }
 
 function write64BitUint (buf, offset, num) {
-  var lo = num % 4294967296
-  var hi = Math.floor(num / 4294967296)
+  const lo = num % 4294967296
+  const hi = Math.floor(num / 4294967296)
 
   buf.writeUInt32BE(hi, offset + 0)
   buf.writeUInt32BE(lo, offset + 4)
 }
 
 function write64BitInt (buf, offset, num) {
-  var negate = num < 0
+  const negate = num < 0
   num = Math.abs(num)
   write64BitUint(buf, offset, num)
   if (negate) negate64BitInt(buf, offset)
 }
 
 function negate64BitInt (buf, offset) {
-  var i = offset + 8
+  let i = offset + 8
 
   // Optimization based on the fact that:
   // buf[i] == 0x00  => (buf[i] ^ 0xff) + 1 = 0x100 = 0x00 + 1 curry
@@ -131,7 +131,7 @@ function negate64BitInt (buf, offset) {
 const fround = Math.fround
 
 function encodeFloat (obj, forceFloat64) {
-  var buf
+  let buf
 
   if (forceFloat64 || !fround || !Object.is(fround(obj), obj)) {
     buf = Buffer.allocUnsafe(9)
@@ -152,25 +152,25 @@ function encodeExt (obj, encodingTypes) {
   const encoded = codec.encode(obj)
   if (!encoded) return null
 
-  return bl([ getExtHeader(encoded.length - 1), encoded ])
+  return bl([getExtHeader(encoded.length - 1), encoded])
 }
 
 function getExtHeader (length) {
-  if (length === 1) return Buffer.from([ 0xd4 ])
-  if (length === 2) return Buffer.from([ 0xd5 ])
-  if (length === 4) return Buffer.from([ 0xd6 ])
-  if (length === 8) return Buffer.from([ 0xd7 ])
-  if (length === 16) return Buffer.from([ 0xd8 ])
-
-  if (length < 256) return Buffer.from([ 0xc7, length ])
-  if (length < 0x10000) return Buffer.from([ 0xc8, length >> 8, length & 0x00ff ])
-  return Buffer.from([ 0xc9, length >> 24, (length >> 16) & 0x000000ff, (length >> 8) & 0x000000ff, length & 0x000000ff ])
+  if (length === 1) return Buffer.from([0xd4])
+  if (length === 2) return Buffer.from([0xd5])
+  if (length === 4) return Buffer.from([0xd6])
+  if (length === 8) return Buffer.from([0xd7])
+  if (length === 16) return Buffer.from([0xd8])
+
+  if (length < 256) return Buffer.from([0xc7, length])
+  if (length < 0x10000) return Buffer.from([0xc8, length >> 8, length & 0x00ff])
+  return Buffer.from([0xc9, length >> 24, (length >> 16) & 0x000000ff, (length >> 8) & 0x000000ff, length & 0x000000ff])
 }
 
 function getHeader (length, tag1, tag2) {
-  if (length < 16) return Buffer.from([ tag1 | length ])
+  if (length < 16) return Buffer.from([tag1 | length])
   const size = length < 0x10000 ? 2 : 4
-  var buf = Buffer.allocUnsafe(1 + size)
+  const buf = Buffer.allocUnsafe(1 + size)
   buf[0] = length < 0x10000 ? tag2 : tag2 + 1
   buf.writeUIntBE(length, 1, size)
 
@@ -179,7 +179,7 @@ function getHeader (length, tag1, tag2) {
 
 function encodeString (obj, options) {
   const len = Buffer.byteLength(obj)
-  var buf
+  let buf
   if (len < 32) {
     buf = Buffer.allocUnsafe(1 + len)
     buf[0] = 0xa0 | len
@@ -207,7 +207,7 @@ function encodeString (obj, options) {
 }
 
 function getBufferHeader (length) {
-  var header
+  let header
   if (length <= 0xff) {
     header = Buffer.allocUnsafe(2)
     header[0] = 0xc4
@@ -226,7 +226,7 @@ function getBufferHeader (length) {
 }
 
 function encodeNumber (obj, options) {
-  var buf
+  let buf
   if (isFloat(obj)) return encodeFloat(obj, options.forceFloat64)
   if (Math.abs(obj) > 9007199254740991) {
     return encodeFloat(obj, true)
@@ -234,13 +234,13 @@ function encodeNumber (obj, options) {
 
   if (obj >= 0) {
     if (obj < 128) {
-      return Buffer.from([ obj ])
+      return Buffer.from([obj])
     } else if (obj < 256) {
-      return Buffer.from([ 0xcc, obj ])
+      return Buffer.from([0xcc, obj])
     } else if (obj < 65536) {
-      return Buffer.from([ 0xcd, 0xff & (obj >> 8), 0xff & (obj) ])
+      return Buffer.from([0xcd, 0xff & (obj >> 8), 0xff & (obj)])
     } else if (obj <= 0xffffffff) {
-      return Buffer.from([ 0xce, 0xff & (obj >> 24), 0xff & (obj >> 16), 0xff & (obj >> 8), 0xff & (obj) ])
+      return Buffer.from([0xce, 0xff & (obj >> 24), 0xff & (obj >> 16), 0xff & (obj >> 8), 0xff & (obj)])
     } else if (obj <= 9007199254740991) {
       buf = Buffer.allocUnsafe(9)
       buf[0] = 0xcf
diff --git a/lib/helpers.js b/lib/helpers.js
index e6e4224..26fdf21 100644
--- a/lib/helpers.js
+++ b/lib/helpers.js
@@ -1,6 +1,6 @@
 'use strict'
 
-var util = require('util')
+const util = require('util')
 
 exports.IncompleteBufferError = IncompleteBufferError
 
diff --git a/lib/streams.js b/lib/streams.js
index 489996e..714f798 100644
--- a/lib/streams.js
+++ b/lib/streams.js
@@ -1,8 +1,8 @@
 'use strict'
 
-var Transform = require('readable-stream').Transform
-var inherits = require('inherits')
-var bl = require('bl')
+const Transform = require('readable-stream').Transform
+const inherits = require('inherits')
+const bl = require('bl')
 
 function Base (opts) {
   opts = opts || {}
@@ -31,7 +31,7 @@ function Encoder (opts) {
 inherits(Encoder, Base)
 
 Encoder.prototype._transform = function (obj, enc, done) {
-  var buf = null
+  let buf = null
 
   try {
     buf = this._msgpack.encode(this._wrap ? obj.value : obj).slice(0)
@@ -65,9 +65,9 @@ Decoder.prototype._transform = function (buf, enc, done) {
   }
 
   try {
-    var result = this._msgpack.decode(this._chunks)
+    let result = this._msgpack.decode(this._chunks)
     if (this._wrap) {
-      result = {value: result}
+      result = { value: result }
     }
     this.push(result)
   } catch (err) {
diff --git a/package.json b/package.json
index d467300..6bc9173 100644
--- a/package.json
+++ b/package.json
@@ -30,12 +30,12 @@
   },
   "homepage": "https://github.com/mcollina/msgpack5",
   "devDependencies": {
-    "browserify": "^16.2.0",
+    "browserify": "^17.0.0",
     "memdb": "^1.3.1",
     "pre-commit": "^1.2.2",
-    "standard": "^11.0.1",
-    "tap-mocha-reporter": "^3.0.7",
-    "tape": "^4.9.1",
+    "standard": "^16.0.0",
+    "tap-mocha-reporter": "^5.0.0",
+    "tape": "^5.0.0",
     "uglify-js": "^3.4.9"
   },
   "standard": {
@@ -44,9 +44,9 @@
     ]
   },
   "dependencies": {
-    "bl": "^2.0.1",
+    "bl": "^4.0.0",
     "inherits": "^2.0.3",
-    "readable-stream": "^2.3.6",
+    "readable-stream": "^3.0.0",
     "safe-buffer": "^5.1.2"
   }
 }
diff --git a/test/1-byte-length-buffers.js b/test/1-byte-length-buffers.js
index b65fe90..701b88d 100644
--- a/test/1-byte-length-buffers.js
+++ b/test/1-byte-length-buffers.js
@@ -1,22 +1,20 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 function build (size) {
-  var buf
-
-  buf = Buffer.allocUnsafe(size)
+  const buf = Buffer.allocUnsafe(size)
   buf.fill('a')
 
   return buf
 }
 
 test('encode/decode 2^8-1 bytes buffers', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   all.push(build(Math.pow(2, 8) - 1))
   all.push(build(Math.pow(2, 6) + 1))
@@ -25,7 +23,7 @@ test('encode/decode 2^8-1 bytes buffers', function (t) {
 
   all.forEach(function (orig) {
     t.test('encoding a buffer of length ' + orig.length, function (t) {
-      var buf = encoder.encode(orig)
+      const buf = encoder.encode(orig)
       t.equal(buf.length, 2 + orig.length, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xc4, 'must have the proper header')
       t.equal(buf.readUInt8(1), orig.length, 'must include the buf length')
@@ -34,7 +32,7 @@ test('encode/decode 2^8-1 bytes buffers', function (t) {
     })
 
     t.test('decoding a buffer of length ' + orig.length, function (t) {
-      var buf = Buffer.allocUnsafe(2 + orig.length)
+      const buf = Buffer.allocUnsafe(2 + orig.length)
       buf[0] = 0xc4
       buf[1] = orig.length
       orig.copy(buf, 2)
@@ -52,14 +50,14 @@ test('encode/decode 2^8-1 bytes buffers', function (t) {
 })
 
 test('decoding a chopped 2^8-1 bytes buffer', function (t) {
-  var encoder = msgpack()
-  var orig = build(Math.pow(2, 6))
-  var buf = Buffer.allocUnsafe(2 + orig.length)
+  const encoder = msgpack()
+  const orig = build(Math.pow(2, 6))
+  let buf = Buffer.allocUnsafe(2 + orig.length)
   buf[0] = 0xc4
   buf[1] = Math.pow(2, 8) - 1 // set bigger size
   orig.copy(buf, 2)
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
@@ -68,11 +66,11 @@ test('decoding a chopped 2^8-1 bytes buffer', function (t) {
 })
 
 test('decoding an incomplete header of 2^8-1 bytes buffer', function (t) {
-  var encoder = msgpack()
-  var buf = Buffer.allocUnsafe(1)
+  const encoder = msgpack()
+  let buf = Buffer.allocUnsafe(1)
   buf[0] = 0xc4
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/1-byte-length-exts.js b/test/1-byte-length-exts.js
index ff24ac3..6066bbc 100644
--- a/test/1-byte-length-exts.js
+++ b/test/1-byte-length-exts.js
@@ -1,13 +1,13 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 test('encode/decode variable ext data up to 0xff', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   function MyType (size, value) {
     this.value = value
@@ -15,15 +15,15 @@ test('encode/decode variable ext data up to 0xff', function (t) {
   }
 
   function mytipeEncode (obj) {
-    var buf = Buffer.allocUnsafe(obj.size)
+    const buf = Buffer.allocUnsafe(obj.size)
     buf.fill(obj.value)
     return buf
   }
 
   function mytipeDecode (data) {
-    var result = new MyType(data.length, data.toString('utf8', 0, 1))
+    const result = new MyType(data.length, data.toString('utf8', 0, 1))
 
-    for (var i = 0; i < data.length; i++) {
+    for (let i = 0; i < data.length; i++) {
       if (data.readUInt8(0) !== data.readUInt8(i)) {
         throw new Error('should all be the same')
       }
@@ -56,7 +56,7 @@ test('encode/decode variable ext data up to 0xff', function (t) {
 
   all.forEach(function (orig) {
     t.test('encoding a custom obj of length ' + orig.size, function (t) {
-      var buf = encoder.encode(orig)
+      const buf = encoder.encode(orig)
       t.equal(buf.length, 3 + orig.size, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xc7, 'must have the ext header')
       t.equal(buf.readUInt8(1), orig.size, 'must include the data length')
@@ -72,13 +72,13 @@ test('encode/decode variable ext data up to 0xff', function (t) {
   })
 
   t.test('decoding an incomplete variable ext data up to 0xff', function (t) {
-    var obj = encoder.encode(new MyType(250, 'a'))
-    var buf = Buffer.allocUnsafe(obj.length)
+    const obj = encoder.encode(new MyType(250, 'a'))
+    let buf = Buffer.allocUnsafe(obj.length)
     buf[0] = 0xc7
     buf.writeUInt8(obj.length + 2, 1) // set bigger size
     obj.copy(buf, 2, 2, obj.length)
     buf = bl().append(buf)
-    var origLength = buf.length
+    const origLength = buf.length
     t.throws(function () {
       encoder.decode(buf)
     }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
@@ -87,10 +87,10 @@ test('encode/decode variable ext data up to 0xff', function (t) {
   })
 
   t.test('decoding an incomplete header of variable ext data up to 0xff', function (t) {
-    var buf = Buffer.allocUnsafe(2)
+    let buf = Buffer.allocUnsafe(2)
     buf[0] = 0xc7
     buf = bl().append(buf)
-    var origLength = buf.length
+    const origLength = buf.length
     t.throws(function () {
       encoder.decode(buf)
     }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/1-byte-length-strings.js b/test/1-byte-length-strings.js
index c79396a..d5efbe4 100644
--- a/test/1-byte-length-strings.js
+++ b/test/1-byte-length-strings.js
@@ -1,17 +1,18 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 test('encode/decode 32 <-> (2^8-1) bytes strings', function (t) {
-  var encoder = msgpack()
-  var all = []
-  var i
+  const encoder = msgpack()
+  const all = []
+  let i
 
   // build base
-  for (i = 'a'; i.length < 32; i += 'a') {
+  for (i = 'a'; i.length < 32;) {
+    i += 'a'
   }
 
   for (; i.length < Math.pow(2, 8); i += 'aaaaa') {
@@ -20,7 +21,7 @@ test('encode/decode 32 <-> (2^8-1) bytes strings', function (t) {
 
   all.forEach(function (str) {
     t.test('encoding a string of length ' + str.length, function (t) {
-      var buf = encoder.encode(str)
+      const buf = encoder.encode(str)
       t.equal(buf.length, 2 + Buffer.byteLength(str), 'must be the proper length')
       t.equal(buf.readUInt8(0), 0xd9, 'must have the proper header')
       t.equal(buf.readUInt8(1), Buffer.byteLength(str), 'must include the str length')
@@ -29,7 +30,7 @@ test('encode/decode 32 <-> (2^8-1) bytes strings', function (t) {
     })
 
     t.test('decoding a string of length ' + str.length, function (t) {
-      var buf = Buffer.allocUnsafe(2 + Buffer.byteLength(str))
+      const buf = Buffer.allocUnsafe(2 + Buffer.byteLength(str))
       buf[0] = 0xd9
       buf[1] = Buffer.byteLength(str)
       buf.write(str, 2)
@@ -47,16 +48,17 @@ test('encode/decode 32 <-> (2^8-1) bytes strings', function (t) {
 })
 
 test('decoding a chopped string', function (t) {
-  var encoder = msgpack()
-  var str
-  for (str = 'a'; str.length < 40; str += 'a') {
+  const encoder = msgpack()
+  let str
+  for (str = 'a'; str.length < 40;) {
+    str += 'a'
   }
-  var buf = Buffer.allocUnsafe(2 + Buffer.byteLength(str))
+  let buf = Buffer.allocUnsafe(2 + Buffer.byteLength(str))
   buf[0] = 0xd9
   buf[1] = Buffer.byteLength(str) + 10 // set bigger size
   buf.write(str, 2)
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
@@ -65,11 +67,11 @@ test('decoding a chopped string', function (t) {
 })
 
 test('decoding an incomplete header of a string', function (t) {
-  var encoder = msgpack()
-  var buf = Buffer.allocUnsafe(1)
+  const encoder = msgpack()
+  let buf = Buffer.allocUnsafe(1)
   buf[0] = 0xd9
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/1-byte-length-uint8arrays.js b/test/1-byte-length-uint8arrays.js
index 2985bf0..3b62539 100644
--- a/test/1-byte-length-uint8arrays.js
+++ b/test/1-byte-length-uint8arrays.js
@@ -1,12 +1,12 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
 
 function build (size) {
-  var array = []
-  var i
+  const array = []
+  let i
 
   for (i = 0; i < size; i++) {
     array.push(42)
@@ -16,8 +16,8 @@ function build (size) {
 }
 
 test('encode/decode 2^8-1 Uint8Arrays', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   all.push(build(Math.pow(2, 8) - 1))
   all.push(build(Math.pow(2, 6) + 1))
@@ -26,7 +26,7 @@ test('encode/decode 2^8-1 Uint8Arrays', function (t) {
 
   all.forEach(function (array) {
     t.test('encoding Uint8Array of length ' + array.byteLength + ' bytes', function (t) {
-      var buf = encoder.encode(array)
+      const buf = encoder.encode(array)
       t.equal(buf.length, 2 + array.byteLength, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xc4, 'must have the proper header')
       t.equal(buf.readUInt8(1), array.byteLength, 'must include the buf length')
diff --git a/test/15-elements-arrays.js b/test/15-elements-arrays.js
index e24e5e1..bf76904 100644
--- a/test/15-elements-arrays.js
+++ b/test/15-elements-arrays.js
@@ -1,13 +1,13 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 function build (size, obj) {
-  var array = []
-  var i
+  const array = []
+  let i
 
   for (i = 0; i < size; i++) {
     array.push(obj)
@@ -17,8 +17,8 @@ function build (size, obj) {
 }
 
 function computeLength (array) {
-  var length = 1 // the header
-  var multi = 1
+  let length = 1 // the header
+  let multi = 1
 
   if (array[0] && typeof array[0] === 'string') {
     multi += array[0].length
@@ -30,9 +30,9 @@ function computeLength (array) {
 }
 
 test('encode/decode arrays up to 15 elements', function (t) {
-  var encoder = msgpack()
-  var all = []
-  var i
+  const encoder = msgpack()
+  const all = []
+  let i
 
   for (i = 0; i < 16; i++) {
     all.push(build(i, 42))
@@ -44,7 +44,7 @@ test('encode/decode arrays up to 15 elements', function (t) {
 
   all.forEach(function (array) {
     t.test('encoding an array with ' + array.length + ' elements of ' + array[0], function (t) {
-      var buf = encoder.encode(array)
+      const buf = encoder.encode(array)
       // the array is full of 1-byte integers
       t.equal(buf.length, computeLength(array), 'must have the right length')
       t.equal(buf.readUInt8(0) & 0xf0, 0x90, 'must have the proper header')
@@ -62,20 +62,20 @@ test('encode/decode arrays up to 15 elements', function (t) {
 })
 
 test('decoding an incomplete array', function (t) {
-  var encoder = msgpack()
+  const encoder = msgpack()
 
-  var array = ['a', 'b', 'c']
-  var size = computeLength(array)
-  var buf = Buffer.allocUnsafe(size)
+  const array = ['a', 'b', 'c']
+  const size = computeLength(array)
+  let buf = Buffer.allocUnsafe(size)
   buf[0] = 0x90 | array.length + 2 // set bigger size
-  var pos = 1
-  for (var i = 0; i < array.length; i++) {
-    var obj = encoder.encode(array[i], true)
+  let pos = 1
+  for (let i = 0; i < array.length; i++) {
+    const obj = encoder.encode(array[i], true)
     obj.copy(buf, pos)
     pos += obj.length
   }
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/15-elements-maps.js b/test/15-elements-maps.js
index 0c72545..8506c0f 100644
--- a/test/15-elements-maps.js
+++ b/test/15-elements-maps.js
@@ -1,13 +1,13 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 function build (size, value) {
-  var map = {}
-  var i
+  const map = {}
+  let i
 
   for (i = 0; i < size; i++) {
     map[i + 100 + ''] = value
@@ -17,8 +17,8 @@ function build (size, value) {
 }
 
 function computeLength (map) {
-  var length = 1 // the header
-  var multi = 5 // we have 4 bytes for each key, plus 1 byte for the value
+  let length = 1 // the header
+  let multi = 5 // we have 4 bytes for each key, plus 1 byte for the value
 
   if (map[100] && typeof map[100] === 'string') {
     multi += map[100].length
@@ -30,9 +30,9 @@ function computeLength (map) {
 }
 
 test('encode/decode maps up to 15 elements', function (t) {
-  var encoder = msgpack()
-  var all = []
-  var i
+  const encoder = msgpack()
+  const all = []
+  let i
 
   for (i = 0; i < 16; i++) {
     all.push(build(i, 42))
@@ -43,9 +43,9 @@ test('encode/decode maps up to 15 elements', function (t) {
   }
 
   all.forEach(function (map) {
-    var length = Object.keys(map).length
+    const length = Object.keys(map).length
     t.test('encoding a map with ' + length + ' elements of ' + map[100], function (t) {
-      var buf = encoder.encode(map)
+      const buf = encoder.encode(map)
       t.equal(buf.length, computeLength(map), 'must have the right length')
       t.equal(buf.readUInt8(0) & 0xf0, 0x80, 'must have the proper header')
       t.equal(buf.readUInt8(0) & 0x0f, length, 'must include the map length')
@@ -62,24 +62,24 @@ test('encode/decode maps up to 15 elements', function (t) {
 })
 
 test('do not encode undefined in a map', function (t) {
-  var instance = msgpack()
-  var expected = { hello: 'world' }
-  var toEncode = { a: undefined, hello: 'world' }
-  var buf = instance.encode(toEncode)
+  const instance = msgpack()
+  const expected = { hello: 'world' }
+  const toEncode = { a: undefined, hello: 'world' }
+  const buf = instance.encode(toEncode)
 
   t.deepEqual(expected, instance.decode(buf), 'must ignore undefined')
   t.end()
 })
 
 test('encode NaN in a map', function (t) {
-  var instance = msgpack()
-  var toEncode = { a: NaN, hello: 'world' }
+  const instance = msgpack()
+  const toEncode = { a: NaN, hello: 'world' }
 
   const buf = instance.encode(toEncode)
 
   t.assert(Object.is(instance.decode(buf).a, NaN))
 
-  const expected = {...toEncode}
+  const expected = { ...toEncode }
   delete toEncode.a
   const actual = instance.decode(buf)
   delete buf.a
@@ -90,27 +90,27 @@ test('encode NaN in a map', function (t) {
 })
 
 test('encode/decode map with buf, ints and strings', function (t) {
-  var map = {
+  const map = {
     topic: 'hello',
     qos: 1,
     payload: Buffer.from('world'),
     messageId: '42',
     ttl: 1416309270167
   }
-  var pack = msgpack()
+  const pack = msgpack()
 
   t.deepEqual(pack.decode(pack.encode(map)), map)
   t.end()
 })
 
 test('decoding a chopped map', function (t) {
-  var encoder = msgpack()
-  var map = encoder.encode({'a': 'b', 'c': 'd', 'e': 'f'})
-  var buf = Buffer.allocUnsafe(map.length)
+  const encoder = msgpack()
+  const map = encoder.encode({ a: 'b', c: 'd', e: 'f' })
+  let buf = Buffer.allocUnsafe(map.length)
   buf[0] = 0x80 | 5 // set bigger size
   map.copy(buf, 1, 1, map.length)
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/16-bits-signed-integers.js b/test/16-bits-signed-integers.js
index 0075a11..0b2a545 100644
--- a/test/16-bits-signed-integers.js
+++ b/test/16-bits-signed-integers.js
@@ -1,14 +1,14 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 test('encoding/decoding 16-bits big-endian signed integers', function (t) {
-  var encoder = msgpack()
-  var allNum = []
-  var i
+  const encoder = msgpack()
+  const allNum = []
+  let i
 
   for (i = 129; i < 32768; i += 1423) {
     allNum.push(-i)
@@ -18,7 +18,7 @@ test('encoding/decoding 16-bits big-endian signed integers', function (t) {
 
   allNum.forEach(function (num) {
     t.test('encoding ' + num, function (t) {
-      var buf = encoder.encode(num)
+      const buf = encoder.encode(num)
       t.equal(buf.length, 3, 'must have 3 bytes')
       t.equal(buf[0], 0xd1, 'must have the proper header')
       t.equal(buf.readInt16BE(1), num, 'must decode correctly')
@@ -26,7 +26,7 @@ test('encoding/decoding 16-bits big-endian signed integers', function (t) {
     })
 
     t.test('decoding ' + num, function (t) {
-      var buf = Buffer.allocUnsafe(3)
+      const buf = Buffer.allocUnsafe(3)
       buf[0] = 0xd1
       buf.writeInt16BE(num, 1)
       t.equal(encoder.decode(buf), num, 'must decode correctly')
@@ -43,11 +43,11 @@ test('encoding/decoding 16-bits big-endian signed integers', function (t) {
 })
 
 test('decoding an incomplete 16-bits big-endian integer', function (t) {
-  var encoder = msgpack()
-  var buf = Buffer.allocUnsafe(2)
+  const encoder = msgpack()
+  let buf = Buffer.allocUnsafe(2)
   buf[0] = 0xd1
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/16-bits-unsigned-integers.js b/test/16-bits-unsigned-integers.js
index 3864cd7..78d5908 100644
--- a/test/16-bits-unsigned-integers.js
+++ b/test/16-bits-unsigned-integers.js
@@ -1,14 +1,14 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 test('encoding/decoding 16-bits big-endian unsigned integers', function (t) {
-  var encoder = msgpack()
-  var allNum = []
-  var i
+  const encoder = msgpack()
+  const allNum = []
+  let i
 
   for (i = 256; i < 65536; i += 1423) {
     allNum.push(i)
@@ -18,7 +18,7 @@ test('encoding/decoding 16-bits big-endian unsigned integers', function (t) {
 
   allNum.forEach(function (num) {
     t.test('encoding ' + num, function (t) {
-      var buf = encoder.encode(num)
+      const buf = encoder.encode(num)
       t.equal(buf.length, 3, 'must have 3 bytes')
       t.equal(buf[0], 0xcd, 'must have the proper header')
       t.equal(buf.readUInt16BE(1), num, 'must decode correctly')
@@ -26,7 +26,7 @@ test('encoding/decoding 16-bits big-endian unsigned integers', function (t) {
     })
 
     t.test('decoding ' + num, function (t) {
-      var buf = Buffer.allocUnsafe(3)
+      const buf = Buffer.allocUnsafe(3)
       buf[0] = 0xcd
       buf.writeUInt16BE(num, 1)
       t.equal(encoder.decode(buf), num, 'must decode correctly')
@@ -43,11 +43,11 @@ test('encoding/decoding 16-bits big-endian unsigned integers', function (t) {
 })
 
 test('decoding an incomplete 16-bits big-endian unsigned integer', function (t) {
-  var encoder = msgpack()
-  var buf = Buffer.allocUnsafe(2)
+  const encoder = msgpack()
+  let buf = Buffer.allocUnsafe(2)
   buf[0] = 0xcd
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/2-bytes-length-arrays.js b/test/2-bytes-length-arrays.js
index 0847d39..5ff658b 100644
--- a/test/2-bytes-length-arrays.js
+++ b/test/2-bytes-length-arrays.js
@@ -1,13 +1,13 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 function build (size) {
-  var array = []
-  var i
+  const array = []
+  let i
 
   for (i = 0; i < size; i++) {
     array.push(42)
@@ -17,9 +17,9 @@ function build (size) {
 }
 
 test('encode/decode arrays up to 0xffff elements', function (t) {
-  var encoder = msgpack()
-  var all = []
-  var i
+  const encoder = msgpack()
+  const all = []
+  let i
 
   for (i = 16; i < 0xffff; i += 4242) {
     all.push(build(i))
@@ -30,7 +30,7 @@ test('encode/decode arrays up to 0xffff elements', function (t) {
 
   all.forEach(function (array) {
     t.test('encoding an array with ' + array.length + ' elements', function (t) {
-      var buf = encoder.encode(array)
+      const buf = encoder.encode(array)
       // the array is full of 1-byte integers
       t.equal(buf.length, 3 + array.length, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xdc, 'must have the proper header')
@@ -48,20 +48,20 @@ test('encode/decode arrays up to 0xffff elements', function (t) {
 })
 
 test('decoding an incomplete array', function (t) {
-  var encoder = msgpack()
+  const encoder = msgpack()
 
-  var array = build(0xffff / 2)
-  var buf = Buffer.allocUnsafe(3 + array.length)
+  const array = build(0xffff / 2)
+  let buf = Buffer.allocUnsafe(3 + array.length)
   buf[0] = 0xdc
   buf.writeUInt16BE(array.length + 10, 1) // set bigger size
-  var pos = 3
-  for (var i = 0; i < array.length; i++) {
-    var obj = encoder.encode(array[i], true)
+  let pos = 3
+  for (let i = 0; i < array.length; i++) {
+    const obj = encoder.encode(array[i], true)
     obj.copy(buf, pos)
     pos += obj.length
   }
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
@@ -70,12 +70,12 @@ test('decoding an incomplete array', function (t) {
 })
 
 test('decoding an incomplete header', function (t) {
-  var encoder = msgpack()
+  const encoder = msgpack()
 
-  var buf = Buffer.allocUnsafe(2)
+  let buf = Buffer.allocUnsafe(2)
   buf[0] = 0xdc
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/2-bytes-length-buffers.js b/test/2-bytes-length-buffers.js
index c1123ec..5fdc3ee 100644
--- a/test/2-bytes-length-buffers.js
+++ b/test/2-bytes-length-buffers.js
@@ -1,22 +1,20 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 function build (size) {
-  var buf
-
-  buf = Buffer.allocUnsafe(size)
+  const buf = Buffer.allocUnsafe(size)
   buf.fill('a')
 
   return buf
 }
 
 test('encode/decode 2^16-1 bytes buffers', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   all.push(build(Math.pow(2, 8)))
   all.push(build(Math.pow(2, 8) + 1))
@@ -25,7 +23,7 @@ test('encode/decode 2^16-1 bytes buffers', function (t) {
 
   all.forEach(function (orig) {
     t.test('encoding a buffer of length ' + orig.length, function (t) {
-      var buf = encoder.encode(orig)
+      const buf = encoder.encode(orig)
       t.equal(buf.length, 3 + orig.length, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xc5, 'must have the proper header')
       t.equal(buf.readUInt16BE(1), orig.length, 'must include the buf length')
@@ -34,7 +32,7 @@ test('encode/decode 2^16-1 bytes buffers', function (t) {
     })
 
     t.test('decoding a buffer of length ' + orig.length, function (t) {
-      var buf = Buffer.allocUnsafe(3 + orig.length)
+      const buf = Buffer.allocUnsafe(3 + orig.length)
       buf[0] = 0xc5
       buf.writeUInt16BE(orig.length, 1)
       orig.copy(buf, 3)
@@ -52,14 +50,14 @@ test('encode/decode 2^16-1 bytes buffers', function (t) {
 })
 
 test('decoding a chopped 2^16-1 bytes buffer', function (t) {
-  var encoder = msgpack()
-  var orig = build(Math.pow(2, 12))
-  var buf = Buffer.allocUnsafe(3 + orig.length)
+  const encoder = msgpack()
+  const orig = build(Math.pow(2, 12))
+  let buf = Buffer.allocUnsafe(3 + orig.length)
   buf[0] = 0xc5
   buf[1] = Math.pow(2, 16) - 1 // set bigger size
   orig.copy(buf, 3)
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
@@ -68,11 +66,11 @@ test('decoding a chopped 2^16-1 bytes buffer', function (t) {
 })
 
 test('decoding an incomplete header of 2^16-1 bytes buffer', function (t) {
-  var encoder = msgpack()
-  var buf = Buffer.allocUnsafe(2)
+  const encoder = msgpack()
+  let buf = Buffer.allocUnsafe(2)
   buf[0] = 0xc5
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/2-bytes-length-exts.js b/test/2-bytes-length-exts.js
index 49593c9..f5aefb6 100644
--- a/test/2-bytes-length-exts.js
+++ b/test/2-bytes-length-exts.js
@@ -1,13 +1,13 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 test('encode/decode variable ext data up between 0x0100 and 0xffff', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   function MyType (size, value) {
     this.value = value
@@ -15,15 +15,15 @@ test('encode/decode variable ext data up between 0x0100 and 0xffff', function (t
   }
 
   function mytipeEncode (obj) {
-    var buf = Buffer.allocUnsafe(obj.size)
+    const buf = Buffer.allocUnsafe(obj.size)
     buf.fill(obj.value)
     return buf
   }
 
   function mytipeDecode (data) {
-    var result = new MyType(data.length, data.toString('utf8', 0, 1))
+    const result = new MyType(data.length, data.toString('utf8', 0, 1))
 
-    for (var i = 0; i < data.length; i++) {
+    for (let i = 0; i < data.length; i++) {
       if (data.readUInt8(0) !== data.readUInt8(i)) {
         throw new Error('should all be the same')
       }
@@ -40,7 +40,7 @@ test('encode/decode variable ext data up between 0x0100 and 0xffff', function (t
 
   all.forEach(function (orig) {
     t.test('encoding a custom obj of length ' + orig.size, function (t) {
-      var buf = encoder.encode(orig)
+      const buf = encoder.encode(orig)
       t.equal(buf.length, 4 + orig.size, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xc8, 'must have the ext header')
       t.equal(buf.readUInt16BE(1), orig.size, 'must include the data length')
@@ -56,13 +56,13 @@ test('encode/decode variable ext data up between 0x0100 and 0xffff', function (t
   })
 
   t.test('decoding an incomplete variable ext data up between 0x0100 and 0xffff', function (t) {
-    var obj = encoder.encode(new MyType(0xfff0, 'a'))
-    var buf = Buffer.allocUnsafe(obj.length)
+    const obj = encoder.encode(new MyType(0xfff0, 'a'))
+    let buf = Buffer.allocUnsafe(obj.length)
     buf[0] = 0xc8
     buf.writeUInt16BE(obj.length + 2, 1) // set bigger size
     obj.copy(buf, 3, 3, obj.length)
     buf = bl().append(buf)
-    var origLength = buf.length
+    const origLength = buf.length
     t.throws(function () {
       encoder.decode(buf)
     }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
@@ -71,10 +71,10 @@ test('encode/decode variable ext data up between 0x0100 and 0xffff', function (t
   })
 
   t.test('decoding an incomplete header of variable ext data up between 0x0100 and 0xffff', function (t) {
-    var buf = Buffer.allocUnsafe(3)
+    let buf = Buffer.allocUnsafe(3)
     buf[0] = 0xc8
     buf = bl().append(buf)
-    var origLength = buf.length
+    const origLength = buf.length
     t.throws(function () {
       encoder.decode(buf)
     }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/2-bytes-length-maps.js b/test/2-bytes-length-maps.js
index dbee52c..0df6321 100644
--- a/test/2-bytes-length-maps.js
+++ b/test/2-bytes-length-maps.js
@@ -1,15 +1,15 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
-var base = 100000
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
+const base = 100000
 
 function build (size, value) {
-  var map = {}
+  const map = {}
 
-  for (var i = 0; i < size; i++) {
+  for (let i = 0; i < size; i++) {
     map[i + base] = value
   }
 
@@ -17,8 +17,8 @@ function build (size, value) {
 }
 
 function computeLength (mapLength) {
-  var length = 3 // the header
-  var multi = ('' + base).length + 1 + 1 // we have <base + 1> bytes for each key, plus 1 byte for the value
+  let length = 3 // the header
+  const multi = ('' + base).length + 1 + 1 // we have <base + 1> bytes for each key, plus 1 byte for the value
 
   length += mapLength * multi
 
@@ -26,11 +26,11 @@ function computeLength (mapLength) {
 }
 
 test('encode/decode maps up to 2^16-1 elements', function (t) {
-  var encoder = msgpack()
+  const encoder = msgpack()
 
   function doTest (length) {
-    var map = build(length, 42)
-    var buf = encoder.encode(map)
+    const map = build(length, 42)
+    const buf = encoder.encode(map)
 
     t.test('encoding a map with ' + length + ' elements of ' + map[base], function (t) {
       // the map is full of 1-byte integers
@@ -56,14 +56,14 @@ test('encode/decode maps up to 2^16-1 elements', function (t) {
 })
 
 test('decoding a chopped map', function (t) {
-  var encoder = msgpack()
-  var map = encoder.encode(build(Math.pow(2, 12) + 1, 42))
-  var buf = Buffer.allocUnsafe(map.length)
+  const encoder = msgpack()
+  const map = encoder.encode(build(Math.pow(2, 12) + 1, 42))
+  let buf = Buffer.allocUnsafe(map.length)
   buf[0] = 0xde
   buf.writeUInt16BE(Math.pow(2, 16) - 1, 1) // set bigger size
   map.copy(buf, 3, 3, map.length)
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
@@ -72,11 +72,11 @@ test('decoding a chopped map', function (t) {
 })
 
 test('decoding an incomplete header of a map', function (t) {
-  var encoder = msgpack()
-  var buf = Buffer.allocUnsafe(2)
+  const encoder = msgpack()
+  let buf = Buffer.allocUnsafe(2)
   buf[0] = 0xde
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/2-bytes-length-strings.js b/test/2-bytes-length-strings.js
index d03a5ad..ee9f8c1 100644
--- a/test/2-bytes-length-strings.js
+++ b/test/2-bytes-length-strings.js
@@ -1,14 +1,14 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 test('encode/decode 2^8 <-> (2^16-1) bytes strings', function (t) {
-  var encoder = msgpack()
-  var all = []
-  var str
+  const encoder = msgpack()
+  const all = []
+  let str
 
   str = Buffer.allocUnsafe(Math.pow(2, 8))
   str.fill('a')
@@ -28,7 +28,7 @@ test('encode/decode 2^8 <-> (2^16-1) bytes strings', function (t) {
 
   all.forEach(function (str) {
     t.test('encoding a string of length ' + str.length, function (t) {
-      var buf = encoder.encode(str)
+      const buf = encoder.encode(str)
       t.equal(buf.length, 3 + Buffer.byteLength(str), 'must be the proper length')
       t.equal(buf[0], 0xda, 'must have the proper header')
       t.equal(buf.readUInt16BE(1), Buffer.byteLength(str), 'must include the str length')
@@ -37,7 +37,7 @@ test('encode/decode 2^8 <-> (2^16-1) bytes strings', function (t) {
     })
 
     t.test('decoding a string of length ' + str.length, function (t) {
-      var buf = Buffer.allocUnsafe(3 + Buffer.byteLength(str))
+      const buf = Buffer.allocUnsafe(3 + Buffer.byteLength(str))
       buf[0] = 0xda
       buf.writeUInt16BE(Buffer.byteLength(str), 1)
       buf.write(str, 3)
@@ -55,16 +55,17 @@ test('encode/decode 2^8 <-> (2^16-1) bytes strings', function (t) {
 })
 
 test('decoding a chopped string', function (t) {
-  var encoder = msgpack()
-  var str
-  for (str = 'a'; str.length < 0xff + 100; str += 'a') {
+  const encoder = msgpack()
+  let str
+  for (str = 'a'; str.length < 0xff + 100;) {
+    str += 'a'
   }
-  var buf = Buffer.allocUnsafe(3 + Buffer.byteLength(str))
+  let buf = Buffer.allocUnsafe(3 + Buffer.byteLength(str))
   buf[0] = 0xda
   buf.writeUInt16BE(Buffer.byteLength(str) + 10, 1) // set bigger size
   buf.write(str, 3)
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
@@ -73,11 +74,11 @@ test('decoding a chopped string', function (t) {
 })
 
 test('decoding an incomplete header of a string', function (t) {
-  var encoder = msgpack()
-  var buf = Buffer.allocUnsafe(2)
+  const encoder = msgpack()
+  let buf = Buffer.allocUnsafe(2)
   buf[0] = 0xda
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/2-bytes-length-uint8arrays.js b/test/2-bytes-length-uint8arrays.js
index f96788a..c824a30 100644
--- a/test/2-bytes-length-uint8arrays.js
+++ b/test/2-bytes-length-uint8arrays.js
@@ -1,12 +1,12 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
 
 function build (size) {
-  var array = []
-  var i
+  const array = []
+  let i
 
   for (i = 0; i < size; i++) {
     array.push(42)
@@ -16,8 +16,8 @@ function build (size) {
 }
 
 test('encode/decode 2^8-1 Uint8Arrays', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   all.push(build(Math.pow(2, 8)))
   all.push(build(Math.pow(2, 8) + 1))
@@ -26,7 +26,7 @@ test('encode/decode 2^8-1 Uint8Arrays', function (t) {
 
   all.forEach(function (array) {
     t.test('encoding Uint8Array of length ' + array.byteLength + ' bytes', function (t) {
-      var buf = encoder.encode(array)
+      const buf = encoder.encode(array)
       t.equal(buf.length, 3 + array.byteLength, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xc5, 'must have the proper header')
       t.equal(buf.readUInt16BE(1), array.byteLength, 'must include the buf length')
diff --git a/test/31-chars-strings.js b/test/31-chars-strings.js
index bb97dd0..239aeb6 100644
--- a/test/31-chars-strings.js
+++ b/test/31-chars-strings.js
@@ -1,22 +1,22 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 test('encode/decode strings with max 31 of length', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   // build base
-  for (var i = ''; i.length < 32; i += 'a') {
+  for (let i = ''; i.length < 32; i += 'a') {
     all.push(i)
   }
 
   all.forEach(function (str) {
     t.test('encoding a string of length ' + str.length, function (t) {
-      var buf = encoder.encode(str)
+      const buf = encoder.encode(str)
       t.equal(buf.length, 1 + Buffer.byteLength(str), 'must be the proper length')
       t.equal(buf.readUInt8(0) & 0xe0, 0xa0, 'must have the proper header')
       t.equal(buf.readUInt8(0) & 0x1f, Buffer.byteLength(str), 'must include the str length')
@@ -25,7 +25,7 @@ test('encode/decode strings with max 31 of length', function (t) {
     })
 
     t.test('decoding a string of length ' + str.length, function (t) {
-      var buf = Buffer.allocUnsafe(1 + Buffer.byteLength(str))
+      const buf = Buffer.allocUnsafe(1 + Buffer.byteLength(str))
       buf[0] = 0xa0 | Buffer.byteLength(str)
       if (str.length > 0) {
         buf.write(str, 1)
@@ -44,13 +44,13 @@ test('encode/decode strings with max 31 of length', function (t) {
 })
 
 test('decoding a chopped string', function (t) {
-  var encoder = msgpack()
-  var str = 'aaa'
-  var buf = Buffer.allocUnsafe(1 + Buffer.byteLength(str))
+  const encoder = msgpack()
+  const str = 'aaa'
+  let buf = Buffer.allocUnsafe(1 + Buffer.byteLength(str))
   buf[0] = 0xa0 | Buffer.byteLength(str) + 2 // set bigger size
   buf.write(str, 1)
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/32-bits-signed-integers.js b/test/32-bits-signed-integers.js
index 75667d0..1bb9c4a 100644
--- a/test/32-bits-signed-integers.js
+++ b/test/32-bits-signed-integers.js
@@ -1,15 +1,15 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 test('encoding/decoding 32-bits big-endian signed integers', function (t) {
-  var encoder = msgpack()
-  var allNum = []
+  const encoder = msgpack()
+  const allNum = []
 
-  for (var i = 32769; i < 214748364; i += 10235023) {
+  for (let i = 32769; i < 214748364; i += 10235023) {
     allNum.push(-i)
   }
 
@@ -17,7 +17,7 @@ test('encoding/decoding 32-bits big-endian signed integers', function (t) {
 
   allNum.forEach(function (num) {
     t.test('encoding ' + num, function (t) {
-      var buf = encoder.encode(num)
+      const buf = encoder.encode(num)
       t.equal(buf.length, 5, 'must have 5 bytes')
       t.equal(buf[0], 0xd2, 'must have the proper header')
       t.equal(buf.readInt32BE(1), num, 'must decode correctly')
@@ -25,7 +25,7 @@ test('encoding/decoding 32-bits big-endian signed integers', function (t) {
     })
 
     t.test('decoding ' + num, function (t) {
-      var buf = Buffer.allocUnsafe(5)
+      const buf = Buffer.allocUnsafe(5)
       buf[0] = 0xd2
       buf.writeInt32BE(num, 1)
       t.equal(encoder.decode(buf), num, 'must decode correctly')
@@ -42,11 +42,11 @@ test('encoding/decoding 32-bits big-endian signed integers', function (t) {
 })
 
 test('decoding an incomplete 32-bits big-endian integer', function (t) {
-  var encoder = msgpack()
-  var buf = Buffer.allocUnsafe(4)
+  const encoder = msgpack()
+  let buf = Buffer.allocUnsafe(4)
   buf[0] = 0xd2
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/32-bits-unsigned-integers.js b/test/32-bits-unsigned-integers.js
index c3be233..4d73505 100644
--- a/test/32-bits-unsigned-integers.js
+++ b/test/32-bits-unsigned-integers.js
@@ -1,15 +1,15 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 test('encoding/decoding 32-bits big-endian unsigned integers', function (t) {
-  var encoder = msgpack()
-  var allNum = []
+  const encoder = msgpack()
+  const allNum = []
 
-  for (var i = 65536; i < 0xffffffff; i += 102350237) {
+  for (let i = 65536; i < 0xffffffff; i += 102350237) {
     allNum.push(i)
   }
 
@@ -18,7 +18,7 @@ test('encoding/decoding 32-bits big-endian unsigned integers', function (t) {
 
   allNum.forEach(function (num) {
     t.test('encoding ' + num, function (t) {
-      var buf = encoder.encode(num)
+      const buf = encoder.encode(num)
       t.equal(buf.length, 5, 'must have 5 bytes')
       t.equal(buf[0], 0xce, 'must have the proper header')
       t.equal(buf.readUInt32BE(1), num, 'must decode correctly')
@@ -26,7 +26,7 @@ test('encoding/decoding 32-bits big-endian unsigned integers', function (t) {
     })
 
     t.test('decoding ' + num, function (t) {
-      var buf = Buffer.allocUnsafe(5)
+      const buf = Buffer.allocUnsafe(5)
       buf[0] = 0xce
       buf.writeUInt32BE(num, 1)
       t.equal(encoder.decode(buf), num, 'must decode correctly')
@@ -43,11 +43,11 @@ test('encoding/decoding 32-bits big-endian unsigned integers', function (t) {
 })
 
 test('decoding an incomplete 32-bits big-endian unsigned integer', function (t) {
-  var encoder = msgpack()
-  var buf = Buffer.allocUnsafe(4)
+  const encoder = msgpack()
+  let buf = Buffer.allocUnsafe(4)
   buf[0] = 0xce
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/32-bytes-strings.js b/test/32-bytes-strings.js
index fce15c0..b9c2d0e 100644
--- a/test/32-bytes-strings.js
+++ b/test/32-bytes-strings.js
@@ -1,20 +1,20 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
 
 test('encode/decode up to 31 bytes strings', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
-  for (var i = 'a'; i.length < 32; i += 'a') {
+  for (let i = 'a'; i.length < 32; i += 'a') {
     all.push(i)
   }
 
   all.forEach(function (str) {
     t.test('encoding a string of length ' + str.length, function (t) {
-      var buf = encoder.encode(str)
+      const buf = encoder.encode(str)
       t.equal(buf.length, 1 + Buffer.byteLength(str), 'must have 2 bytes')
       t.equal(buf[0] & 0xe0, 0xa0, 'must have the proper header')
       t.equal(buf.toString('utf8', 1, Buffer.byteLength(str) + 1), str, 'must decode correctly')
@@ -22,7 +22,7 @@ test('encode/decode up to 31 bytes strings', function (t) {
     })
 
     t.test('decoding a string of length ' + str.length, function (t) {
-      var buf = Buffer.allocUnsafe(1 + Buffer.byteLength(str))
+      const buf = Buffer.allocUnsafe(1 + Buffer.byteLength(str))
       buf[0] = 0xa0 | Buffer.byteLength(str)
       buf.write(str, 1)
       t.equal(encoder.decode(buf), str, 'must decode correctly')
diff --git a/test/4-bytes-length-arrays.js b/test/4-bytes-length-arrays.js
index 0e863fe..46e92cc 100644
--- a/test/4-bytes-length-arrays.js
+++ b/test/4-bytes-length-arrays.js
@@ -1,14 +1,14 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 function build (size) {
-  var array = []
+  const array = []
 
-  for (var i = 0; i < size; i++) {
+  for (let i = 0; i < size; i++) {
     array.push(42)
   }
 
@@ -16,11 +16,11 @@ function build (size) {
 }
 
 test('encode/decode arrays up to 0xffffffff elements', function (t) {
-  var encoder = msgpack()
+  const encoder = msgpack()
 
   function doTest (array) {
     t.test('encoding an array with ' + array.length + ' elements', function (t) {
-      var buf = encoder.encode(array)
+      const buf = encoder.encode(array)
       // the array is full of 1-byte integers
       t.equal(buf.length, 5 + array.length, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xdd, 'must have the proper header')
@@ -42,20 +42,20 @@ test('encode/decode arrays up to 0xffffffff elements', function (t) {
 })
 
 test('decoding an incomplete array', function (t) {
-  var encoder = msgpack()
+  const encoder = msgpack()
 
-  var array = build(0xffff + 42)
-  var buf = Buffer.allocUnsafe(5 + array.length)
+  const array = build(0xffff + 42)
+  let buf = Buffer.allocUnsafe(5 + array.length)
   buf[0] = 0xdd
   buf.writeUInt32BE(array.length + 10, 1) // set bigger size
-  var pos = 5
-  for (var i = 0; i < array.length; i++) {
-    var obj = encoder.encode(array[i], true)
+  let pos = 5
+  for (let i = 0; i < array.length; i++) {
+    const obj = encoder.encode(array[i], true)
     obj.copy(buf, pos)
     pos += obj.length
   }
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
@@ -64,12 +64,12 @@ test('decoding an incomplete array', function (t) {
 })
 
 test('decoding an incomplete header', function (t) {
-  var encoder = msgpack()
+  const encoder = msgpack()
 
-  var buf = Buffer.allocUnsafe(4)
+  let buf = Buffer.allocUnsafe(4)
   buf[0] = 0xdd
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/4-bytes-length-buffers.js b/test/4-bytes-length-buffers.js
index 5e1912b..27749da 100644
--- a/test/4-bytes-length-buffers.js
+++ b/test/4-bytes-length-buffers.js
@@ -1,22 +1,20 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 function build (size) {
-  var buf
-
-  buf = Buffer.allocUnsafe(size)
+  const buf = Buffer.allocUnsafe(size)
   buf.fill('a')
 
   return buf
 }
 
 test('encode/decode 2^32-1 bytes buffers', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   all.push(build(Math.pow(2, 16)))
   all.push(build(Math.pow(2, 16) + 1))
@@ -24,7 +22,7 @@ test('encode/decode 2^32-1 bytes buffers', function (t) {
 
   all.forEach(function (orig) {
     t.test('encoding a buffer of length ' + orig.length, function (t) {
-      var buf = encoder.encode(orig)
+      const buf = encoder.encode(orig)
       t.equal(buf.length, 5 + orig.length, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xc6, 'must have the proper header')
       t.equal(buf.readUInt32BE(1), orig.length, 'must include the buf length')
@@ -33,7 +31,7 @@ test('encode/decode 2^32-1 bytes buffers', function (t) {
     })
 
     t.test('decoding a buffer of length ' + orig.length, function (t) {
-      var buf = Buffer.allocUnsafe(5 + orig.length)
+      const buf = Buffer.allocUnsafe(5 + orig.length)
       buf[0] = 0xc6
       buf.writeUInt32BE(orig.length, 1)
       orig.copy(buf, 5)
@@ -51,14 +49,14 @@ test('encode/decode 2^32-1 bytes buffers', function (t) {
 })
 
 test('decoding a chopped 2^32-1 bytes buffer', function (t) {
-  var encoder = msgpack()
-  var orig = build(Math.pow(2, 18))
-  var buf = Buffer.allocUnsafe(5 + orig.length)
+  const encoder = msgpack()
+  const orig = build(Math.pow(2, 18))
+  let buf = Buffer.allocUnsafe(5 + orig.length)
   buf[0] = 0xc6
   buf[1] = Math.pow(2, 32) - 1 // set bigger size
   orig.copy(buf, 5)
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
@@ -67,11 +65,11 @@ test('decoding a chopped 2^32-1 bytes buffer', function (t) {
 })
 
 test('decoding an incomplete header of 2^32-1 bytes buffer', function (t) {
-  var encoder = msgpack()
-  var buf = Buffer.allocUnsafe(4)
+  const encoder = msgpack()
+  let buf = Buffer.allocUnsafe(4)
   buf[0] = 0xc6
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/4-bytes-length-exts.js b/test/4-bytes-length-exts.js
index 786de82..e1e539f 100644
--- a/test/4-bytes-length-exts.js
+++ b/test/4-bytes-length-exts.js
@@ -1,13 +1,13 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 test('encode/decode variable ext data up between 0x10000 and 0xffffffff', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   function MyType (size, value) {
     this.value = value
@@ -15,15 +15,15 @@ test('encode/decode variable ext data up between 0x10000 and 0xffffffff', functi
   }
 
   function mytipeEncode (obj) {
-    var buf = Buffer.allocUnsafe(obj.size)
+    const buf = Buffer.allocUnsafe(obj.size)
     buf.fill(obj.value)
     return buf
   }
 
   function mytipeDecode (data) {
-    var result = new MyType(data.length, data.toString('utf8', 0, 1))
+    const result = new MyType(data.length, data.toString('utf8', 0, 1))
 
-    for (var i = 0; i < data.length; i++) {
+    for (let i = 0; i < data.length; i++) {
       if (data.readUInt8(0) !== data.readUInt8(i)) {
         throw new Error('should all be the same')
       }
@@ -40,7 +40,7 @@ test('encode/decode variable ext data up between 0x10000 and 0xffffffff', functi
 
   all.forEach(function (orig) {
     t.test('encoding a custom obj of length ' + orig.size, function (t) {
-      var buf = encoder.encode(orig)
+      const buf = encoder.encode(orig)
       t.equal(buf.length, 6 + orig.size, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xc9, 'must have the ext header')
       t.equal(buf.readUInt32BE(1), orig.size, 'must include the data length')
@@ -56,13 +56,13 @@ test('encode/decode variable ext data up between 0x10000 and 0xffffffff', functi
   })
 
   t.test('decoding an incomplete variable ext data up between 0x10000 and 0xffffffff', function (t) {
-    var obj = encoder.encode(new MyType(0xffffff, 'a'))
-    var buf = Buffer.allocUnsafe(obj.length)
+    const obj = encoder.encode(new MyType(0xffffff, 'a'))
+    let buf = Buffer.allocUnsafe(obj.length)
     buf[0] = 0xc9
     buf.writeUInt32BE(obj.length + 2, 1) // set bigger size
     obj.copy(buf, 5, 5, obj.length)
     buf = bl().append(buf)
-    var origLength = buf.length
+    const origLength = buf.length
     t.throws(function () {
       encoder.decode(buf)
     }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
@@ -71,10 +71,10 @@ test('encode/decode variable ext data up between 0x10000 and 0xffffffff', functi
   })
 
   t.test('decoding an incomplete header of variable ext data up between 0x10000 and 0xffffffff', function (t) {
-    var buf = Buffer.allocUnsafe(5)
+    let buf = Buffer.allocUnsafe(5)
     buf[0] = 0xc9
     buf = bl().append(buf)
-    var origLength = buf.length
+    const origLength = buf.length
     t.throws(function () {
       encoder.decode(buf)
     }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/4-bytes-length-strings.js b/test/4-bytes-length-strings.js
index fda7d74..7670151 100644
--- a/test/4-bytes-length-strings.js
+++ b/test/4-bytes-length-strings.js
@@ -1,14 +1,14 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 test('encode/decode 2^16 <-> (2^32 - 1) bytes strings', function (t) {
-  var encoder = msgpack()
-  var all = []
-  var str
+  const encoder = msgpack()
+  const all = []
+  let str
 
   str = Buffer.allocUnsafe(Math.pow(2, 16))
   str.fill('a')
@@ -24,7 +24,7 @@ test('encode/decode 2^16 <-> (2^32 - 1) bytes strings', function (t) {
 
   all.forEach(function (str) {
     t.test('encoding a string of length ' + str.length, function (t) {
-      var buf = encoder.encode(str)
+      const buf = encoder.encode(str)
       t.equal(buf.length, 5 + Buffer.byteLength(str), 'must be the proper length')
       t.equal(buf[0], 0xdb, 'must have the proper header')
       t.equal(buf.readUInt32BE(1), Buffer.byteLength(str), 'must include the str length')
@@ -33,7 +33,7 @@ test('encode/decode 2^16 <-> (2^32 - 1) bytes strings', function (t) {
     })
 
     t.test('decoding a string of length ' + str.length, function (t) {
-      var buf = Buffer.allocUnsafe(5 + Buffer.byteLength(str))
+      const buf = Buffer.allocUnsafe(5 + Buffer.byteLength(str))
       buf[0] = 0xdb
       buf.writeUInt32BE(Buffer.byteLength(str), 1)
       buf.write(str, 5)
@@ -51,16 +51,17 @@ test('encode/decode 2^16 <-> (2^32 - 1) bytes strings', function (t) {
 })
 
 test('decoding a chopped string', function (t) {
-  var encoder = msgpack()
-  var str
-  for (str = 'a'; str.length < 0xffff + 100; str += 'a') {
+  const encoder = msgpack()
+  let str
+  for (str = 'a'; str.length < 0xffff + 100;) {
+    str += 'a'
   }
-  var buf = Buffer.allocUnsafe(5 + Buffer.byteLength(str))
+  let buf = Buffer.allocUnsafe(5 + Buffer.byteLength(str))
   buf[0] = 0xdb
   buf.writeUInt32BE(Buffer.byteLength(str) + 10, 1) // set bigger size
   buf.write(str, 5)
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
@@ -69,11 +70,11 @@ test('decoding a chopped string', function (t) {
 })
 
 test('decoding an incomplete header of a string', function (t) {
-  var encoder = msgpack()
-  var buf = Buffer.allocUnsafe(4)
+  const encoder = msgpack()
+  let buf = Buffer.allocUnsafe(4)
   buf[0] = 0xdb
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/4-bytes-length-uint8arrays.js b/test/4-bytes-length-uint8arrays.js
index ae5961e..46147d9 100644
--- a/test/4-bytes-length-uint8arrays.js
+++ b/test/4-bytes-length-uint8arrays.js
@@ -1,12 +1,12 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
 
 function build (size) {
-  var array = []
-  var i
+  const array = []
+  let i
 
   for (i = 0; i < size; i++) {
     array.push(42)
@@ -16,8 +16,8 @@ function build (size) {
 }
 
 test('encode/decode 2^8-1 Uint8Arrays', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   all.push(build(Math.pow(2, 16)))
   all.push(build(Math.pow(2, 16) + 1))
@@ -25,7 +25,7 @@ test('encode/decode 2^8-1 Uint8Arrays', function (t) {
 
   all.forEach(function (array) {
     t.test('encoding Uint8Array of length ' + array.byteLength + ' bytes', function (t) {
-      var buf = encoder.encode(array)
+      const buf = encoder.encode(array)
       t.equal(buf.length, 5 + array.byteLength, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xc6, 'must have the proper header')
       t.equal(buf.readUInt32BE(1), array.byteLength, 'must include the buf length')
diff --git a/test/5-bits-negative-integers.js b/test/5-bits-negative-integers.js
index 28b8e1e..76d4436 100644
--- a/test/5-bits-negative-integers.js
+++ b/test/5-bits-negative-integers.js
@@ -1,27 +1,27 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
 
 test('encoding/decoding 5-bits negative ints', function (t) {
-  var encoder = msgpack()
-  var allNum = []
+  const encoder = msgpack()
+  const allNum = []
 
-  for (var i = 1; i <= 32; i++) {
+  for (let i = 1; i <= 32; i++) {
     allNum.push(-i)
   }
 
   allNum.forEach(function (num) {
     t.test('encoding ' + num, function (t) {
-      var buf = encoder.encode(num)
+      const buf = encoder.encode(num)
       t.equal(buf.length, 1, 'must have 1 byte')
       t.equal(buf[0], num + 0x100, 'must encode correctly')
       t.end()
     })
 
     t.test('decoding' + num, function (t) {
-      var buf = Buffer.from([num + 0x100])
+      const buf = Buffer.from([num + 0x100])
       t.equal(encoder.decode(buf), num, 'must decode correctly')
       t.end()
     })
diff --git a/test/64-bits-signed-integers.js b/test/64-bits-signed-integers.js
index c68c2b8..86b8342 100644
--- a/test/64-bits-signed-integers.js
+++ b/test/64-bits-signed-integers.js
@@ -1,13 +1,13 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 test('encoding/decoding 64-bits big-endian signed integers', function (t) {
-  var encoder = msgpack()
-  var table = [
+  const encoder = msgpack()
+  const table = [
     { num: -9007199254740991, hi: 0xffe00000, lo: 0x00000001 },
     { num: -4294967297, hi: 0xfffffffe, lo: 0xffffffff },
     { num: -4294967296, hi: 0xffffffff, lo: 0x00000000 },
@@ -17,7 +17,7 @@ test('encoding/decoding 64-bits big-endian signed integers', function (t) {
 
   table.forEach(function (testCase) {
     t.test('encoding ' + testCase.num, function (t) {
-      var buf = encoder.encode(testCase.num)
+      const buf = encoder.encode(testCase.num)
       t.equal(buf.length, 9, 'must have 9 bytes')
       t.equal(buf[0], 0xd3, 'must have the proper header')
       t.equal(buf.readUInt32BE(1), testCase.hi, 'hi word must be properly written')
@@ -35,11 +35,11 @@ test('encoding/decoding 64-bits big-endian signed integers', function (t) {
 })
 
 test('decoding an incomplete 64-bits big-endian signed integer', function (t) {
-  var encoder = msgpack()
-  var buf = Buffer.allocUnsafe(8)
+  const encoder = msgpack()
+  let buf = Buffer.allocUnsafe(8)
   buf[0] = 0xd3
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/64-bits-unsigned-integers.js b/test/64-bits-unsigned-integers.js
index 348a43c..f5d6281 100644
--- a/test/64-bits-unsigned-integers.js
+++ b/test/64-bits-unsigned-integers.js
@@ -1,24 +1,24 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 test('encoding/decoding 64-bits big-endian unsigned integers', function (t) {
-  var encoder = msgpack()
-  var allNum = []
+  const encoder = msgpack()
+  const allNum = []
 
   allNum.push(0x0000000100000000)
   allNum.push(0xffffffffeeeee)
 
   allNum.forEach(function (num) {
     t.test('encoding ' + num, function (t) {
-      var buf = encoder.encode(num)
+      const buf = encoder.encode(num)
       t.equal(buf.length, 9, 'must have 9 bytes')
       t.equal(buf[0], 0xcf, 'must have the proper header')
-      var result = 0
-      for (var k = 7; k >= 0; k--) {
+      let result = 0
+      for (let k = 7; k >= 0; k--) {
         result += (buf.readUInt8(k + 1) * Math.pow(2, (8 * (7 - k))))
       }
       t.equal(result, num, 'must decode correctly')
@@ -35,11 +35,11 @@ test('encoding/decoding 64-bits big-endian unsigned integers', function (t) {
 })
 
 test('decoding an incomplete 64-bits big-endian unsigned integer', function (t) {
-  var encoder = msgpack()
-  var buf = Buffer.allocUnsafe(8)
+  const encoder = msgpack()
+  let buf = Buffer.allocUnsafe(8)
   buf[0] = 0xcf
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/7-bits-positive-integers.js b/test/7-bits-positive-integers.js
index 89a3ab9..16685ea 100644
--- a/test/7-bits-positive-integers.js
+++ b/test/7-bits-positive-integers.js
@@ -1,27 +1,27 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
 
 test('encoding/decoding 7-bits positive ints', function (t) {
-  var encoder = msgpack()
-  var allNum = []
+  const encoder = msgpack()
+  const allNum = []
 
-  for (var i = 0; i < 126; i++) {
+  for (let i = 0; i < 126; i++) {
     allNum.push(i)
   }
 
   allNum.forEach(function (num) {
     t.test('encoding ' + num, function (t) {
-      var buf = encoder.encode(num)
+      const buf = encoder.encode(num)
       t.equal(buf.length, 1, 'must have 1 byte')
       t.equal(buf[0], num, 'must decode correctly')
       t.end()
     })
 
     t.test('decoding ' + num, function (t) {
-      var buf = Buffer.from([num])
+      const buf = Buffer.from([num])
       t.equal(encoder.decode(buf), num, 'must decode correctly')
       t.end()
     })
diff --git a/test/8-bits-positive-integers.js b/test/8-bits-positive-integers.js
index d3ba907..b30fb2c 100644
--- a/test/8-bits-positive-integers.js
+++ b/test/8-bits-positive-integers.js
@@ -1,21 +1,21 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 test('encoding/decoding 8-bits integers', function (t) {
-  var encoder = msgpack()
-  var allNum = []
+  const encoder = msgpack()
+  const allNum = []
 
-  for (var i = 128; i < 256; i++) {
+  for (let i = 128; i < 256; i++) {
     allNum.push(i)
   }
 
   allNum.forEach(function (num) {
     t.test('encoding ' + num, function (t) {
-      var buf = encoder.encode(num)
+      const buf = encoder.encode(num)
       t.equal(buf.length, 2, 'must have 2 bytes')
       t.equal(buf[0], 0xcc, 'must have the proper header')
       t.equal(buf[1], num, 'must decode correctly')
@@ -23,7 +23,7 @@ test('encoding/decoding 8-bits integers', function (t) {
     })
 
     t.test('decoding ' + num, function (t) {
-      var buf = Buffer.from([0xcc, num])
+      const buf = Buffer.from([0xcc, num])
       t.equal(encoder.decode(buf), num, 'must decode correctly')
       t.end()
     })
@@ -38,11 +38,11 @@ test('encoding/decoding 8-bits integers', function (t) {
 })
 
 test('decoding an incomplete 8-bits unsigned integer', function (t) {
-  var encoder = msgpack()
-  var buf = Buffer.allocUnsafe(1)
+  const encoder = msgpack()
+  let buf = Buffer.allocUnsafe(1)
   buf[0] = 0xcc
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/8-bits-signed-integers.js b/test/8-bits-signed-integers.js
index b81e24c..e074d35 100644
--- a/test/8-bits-signed-integers.js
+++ b/test/8-bits-signed-integers.js
@@ -1,21 +1,21 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 test('encoding/decoding 8-bits big-endian signed integers', function (t) {
-  var encoder = msgpack()
-  var allNum = []
+  const encoder = msgpack()
+  const allNum = []
 
-  for (var i = 33; i <= 128; i++) {
+  for (let i = 33; i <= 128; i++) {
     allNum.push(-i)
   }
 
   allNum.forEach(function (num) {
     t.test('encoding ' + num, function (t) {
-      var buf = encoder.encode(num)
+      const buf = encoder.encode(num)
       t.equal(buf.length, 2, 'must have 2 bytes')
       t.equal(buf[0], 0xd0, 'must have the proper header')
       t.equal(buf.readInt8(1), num, 'must decode correctly')
@@ -23,7 +23,7 @@ test('encoding/decoding 8-bits big-endian signed integers', function (t) {
     })
 
     t.test('decoding ' + num, function (t) {
-      var buf = Buffer.allocUnsafe(3)
+      const buf = Buffer.allocUnsafe(3)
       buf[0] = 0xd0
       buf.writeInt8(num, 1)
       t.equal(encoder.decode(buf), num, 'must decode correctly')
@@ -40,11 +40,11 @@ test('encoding/decoding 8-bits big-endian signed integers', function (t) {
 })
 
 test('decoding an incomplete 8-bits big-endian signed integer', function (t) {
-  var encoder = msgpack()
-  var buf = Buffer.allocUnsafe(1)
+  const encoder = msgpack()
+  let buf = Buffer.allocUnsafe(1)
   buf[0] = 0xd0
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/NaN.js b/test/NaN.js
index ba5054b..bf4c1b2 100644
--- a/test/NaN.js
+++ b/test/NaN.js
@@ -1,7 +1,7 @@
 'use strict'
 
-var test = require('tape').test
-var msgpack = require('../')
+const test = require('tape').test
+const msgpack = require('../')
 
 test('encode NaN as 32-bit float', function (t) {
   const encoder = msgpack()
@@ -14,7 +14,7 @@ test('encode NaN as 32-bit float', function (t) {
 })
 
 test('encode NaN as 64-bit float with forceFloat64', function (t) {
-  const encoder = msgpack({forceFloat64: true})
+  const encoder = msgpack({ forceFloat64: true })
 
   const buf = encoder.encode(NaN)
 
@@ -33,7 +33,7 @@ test('round-trip 32-bit NaN', function (t) {
 })
 
 test('round-trip 64-bit NaN with forceFloat64', function (t) {
-  const encoder = msgpack({forceFloat64: true})
+  const encoder = msgpack({ forceFloat64: true })
 
   t.assert(Object.is(encoder.decode(encoder.encode(NaN)), NaN))
 
diff --git a/test/booleans.js b/test/booleans.js
index 8781021..02fb5be 100644
--- a/test/booleans.js
+++ b/test/booleans.js
@@ -1,11 +1,11 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
 
 test('encode/decode booleans', function (t) {
-  var encoder = msgpack()
+  const encoder = msgpack()
 
   t.equal(encoder.encode(true)[0], 0xc3, 'encode true as 0xc3')
   t.equal(encoder.encode(true).length, 1, 'encode true as a buffer of length 1')
diff --git a/test/compatibility-mode.js b/test/compatibility-mode.js
index fdadb12..743fee7 100644
--- a/test/compatibility-mode.js
+++ b/test/compatibility-mode.js
@@ -1,22 +1,22 @@
 'use strict'
 
-var test = require('tape').test
-var msgpack = require('../')
+const test = require('tape').test
+const msgpack = require('../')
 
 test('encode/compatibility mode', function (t) {
-  var compatEncoder = msgpack({
+  const compatEncoder = msgpack({
     compatibilityMode: true
   })
-  var defaultEncoder = msgpack({
+  const defaultEncoder = msgpack({
     compatibilityMode: false
   })
 
-  var oneBytesStr = Array(31 + 2).join('x')
-  var twoBytesStr = Array(255 + 2).join('x')
+  const oneBytesStr = Array(31 + 2).join('x')
+  const twoBytesStr = Array(255 + 2).join('x')
 
   t.test('default encoding a string of length ' + oneBytesStr.length, function (t) {
     // Default: use 1 byte length string (str8)
-    var buf = defaultEncoder.encode(oneBytesStr)
+    const buf = defaultEncoder.encode(oneBytesStr)
     t.equal(buf[0], 0xd9, 'must have the proper header (str8)')
     t.equal(buf.toString('utf8', 2, Buffer.byteLength(oneBytesStr) + 2), oneBytesStr, 'must decode correctly')
     t.end()
@@ -24,7 +24,7 @@ test('encode/compatibility mode', function (t) {
 
   t.test('compat. encoding a string of length ' + oneBytesStr.length, function (t) {
     // Compat. mode: use 2 byte length string (str16)
-    var buf = compatEncoder.encode(oneBytesStr)
+    const buf = compatEncoder.encode(oneBytesStr)
     t.equal(buf[0], 0xda, 'must have the proper header (str16)')
     t.equal(buf.toString('utf8', 3, Buffer.byteLength(oneBytesStr) + 3), oneBytesStr, 'must decode correctly')
     t.end()
@@ -32,8 +32,8 @@ test('encode/compatibility mode', function (t) {
 
   t.test('encoding for a string of length ' + twoBytesStr.length, function (t) {
     // Two byte strings: compat. mode should make no difference
-    var buf1 = defaultEncoder.encode(twoBytesStr)
-    var buf2 = compatEncoder.encode(twoBytesStr)
+    const buf1 = defaultEncoder.encode(twoBytesStr)
+    const buf2 = compatEncoder.encode(twoBytesStr)
     t.deepEqual(buf1, buf2, 'must be equal for two byte strings')
     t.end()
   })
diff --git a/test/datenull.js b/test/datenull.js
index fb9bed9..f193337 100644
--- a/test/datenull.js
+++ b/test/datenull.js
@@ -1,9 +1,9 @@
 'use strict'
-var test = require('tape').test
-var msgpack = require('../')
+const test = require('tape').test
+const msgpack = require('../')
 
 test('encode date is null ', function (t) {
-  var encoder = msgpack({
+  const encoder = msgpack({
     disableTimestampEncoding: true
   })
 
diff --git a/test/doubles.js b/test/doubles.js
index afa0e48..5fe8002 100644
--- a/test/doubles.js
+++ b/test/doubles.js
@@ -1,13 +1,13 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 test('encoding/decoding 64-bits float numbers', function (t) {
-  var encoder = msgpack()
-  var allNum = []
+  const encoder = msgpack()
+  const allNum = []
 
   allNum.push(748365544534.2)
   allNum.push(-222111111000004.2)
@@ -16,8 +16,8 @@ test('encoding/decoding 64-bits float numbers', function (t) {
 
   allNum.forEach(function (num) {
     t.test('encoding ' + num, function (t) {
-      var buf = encoder.encode(num)
-      var dec = buf.readDoubleBE(1)
+      const buf = encoder.encode(num)
+      const dec = buf.readDoubleBE(1)
       t.equal(buf.length, 9, 'must have 9 bytes')
       t.equal(buf[0], 0xcb, 'must have the proper header')
       t.true(Math.abs(dec - num) < 0.1, 'must decode correctly')
@@ -25,17 +25,16 @@ test('encoding/decoding 64-bits float numbers', function (t) {
     })
 
     t.test('decoding ' + num, function (t) {
-      var buf = Buffer.allocUnsafe(9)
-      var dec
+      const buf = Buffer.allocUnsafe(9)
       buf[0] = 0xcb
       buf.writeDoubleBE(num, 1)
-      dec = encoder.decode(buf)
+      const dec = encoder.decode(buf)
       t.true(Math.abs(dec - num) < 0.1, 'must decode correctly')
       t.end()
     })
 
     t.test('mirror test ' + num, function (t) {
-      var dec = encoder.decode(encoder.encode(num))
+      const dec = encoder.decode(encoder.encode(num))
       t.true(Math.abs(dec - num) < 0.1, 'must decode correctly')
       t.end()
     })
@@ -45,11 +44,11 @@ test('encoding/decoding 64-bits float numbers', function (t) {
 })
 
 test('decoding an incomplete 64-bits float numbers', function (t) {
-  var encoder = msgpack()
-  var buf = Buffer.allocUnsafe(8)
+  const encoder = msgpack()
+  let buf = Buffer.allocUnsafe(8)
   buf[0] = 0xcb
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/ext-custom-encode-check.js b/test/ext-custom-encode-check.js
index 3d682c2..22f591f 100644
--- a/test/ext-custom-encode-check.js
+++ b/test/ext-custom-encode-check.js
@@ -1,12 +1,12 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
 
 test('encode/decode ext with a custom object check', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   function MyType (data) {
     this.data = data
@@ -17,7 +17,7 @@ test('encode/decode ext with a custom object check', function (t) {
   }
 
   function mytypeEncode (obj) {
-    var buf = Buffer.allocUnsafe(2)
+    const buf = Buffer.allocUnsafe(2)
     buf.writeUInt8(0x42, 0)
     buf.writeUInt8(obj.data, 1)
     return buf
@@ -36,7 +36,7 @@ test('encode/decode ext with a custom object check', function (t) {
 
   all.forEach(function (orig) {
     t.test('encoding a custom obj encoded as ' + orig.data, function (t) {
-      var buf = encoder.encode(orig)
+      const buf = encoder.encode(orig)
       t.equal(buf.length, 3, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xd4, 'must have the fixext header')
       t.equal(buf.readUInt8(1), 0x42, 'must include the custom type id')
@@ -45,7 +45,7 @@ test('encode/decode ext with a custom object check', function (t) {
     })
 
     t.test('decoding a custom obj encoded as ' + orig.data, function (t) {
-      var buf = Buffer.allocUnsafe(3)
+      const buf = Buffer.allocUnsafe(3)
       buf[0] = 0xd4
       buf[1] = 0x42
       buf.writeUInt8(orig.data, 2)
diff --git a/test/fixexts.js b/test/fixexts.js
index 6fb60f8..c045984 100644
--- a/test/fixexts.js
+++ b/test/fixexts.js
@@ -1,20 +1,20 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 test('encode/decode 1 byte fixext data', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   function MyType (data) {
     this.data = data
   }
 
   function mytypeEncode (obj) {
-    var buf = Buffer.allocUnsafe(1)
+    const buf = Buffer.allocUnsafe(1)
     buf.writeUInt8(obj.data, 0)
     return buf
   }
@@ -31,7 +31,7 @@ test('encode/decode 1 byte fixext data', function (t) {
 
   all.forEach(function (orig) {
     t.test('encoding a custom obj encoded as ' + orig.data, function (t) {
-      var buf = encoder.encode(orig)
+      const buf = encoder.encode(orig)
       t.equal(buf.length, 3, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xd4, 'must have the fixext header')
       t.equal(buf.readUInt8(1), 0x42, 'must include the custom type id')
@@ -40,7 +40,7 @@ test('encode/decode 1 byte fixext data', function (t) {
     })
 
     t.test('decoding a custom obj encoded as ' + orig.data, function (t) {
-      var buf = Buffer.allocUnsafe(3)
+      const buf = Buffer.allocUnsafe(3)
       buf[0] = 0xd4
       buf[1] = 0x42
       buf.writeUInt8(orig.data, 2)
@@ -59,15 +59,15 @@ test('encode/decode 1 byte fixext data', function (t) {
 })
 
 test('encode/decode 2 bytes fixext data', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   function MyType (data) {
     this.data = data
   }
 
   function mytypeEncode (obj) {
-    var buf = Buffer.allocUnsafe(2)
+    const buf = Buffer.allocUnsafe(2)
     buf.writeUInt16BE(obj.data, 0)
     return buf
   }
@@ -84,7 +84,7 @@ test('encode/decode 2 bytes fixext data', function (t) {
 
   all.forEach(function (orig) {
     t.test('encoding a custom obj encoded as ' + orig.data, function (t) {
-      var buf = encoder.encode(orig)
+      const buf = encoder.encode(orig)
       t.equal(buf.length, 4, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xd5, 'must have the fixext header')
       t.equal(buf.readUInt8(1), 0x42, 'must include the custom type id')
@@ -93,7 +93,7 @@ test('encode/decode 2 bytes fixext data', function (t) {
     })
 
     t.test('decoding a custom obj encoded as ' + orig.data, function (t) {
-      var buf = Buffer.allocUnsafe(4)
+      const buf = Buffer.allocUnsafe(4)
       buf[0] = 0xd5
       buf[1] = 0x42
       buf.writeUInt16BE(orig.data, 2)
@@ -112,15 +112,15 @@ test('encode/decode 2 bytes fixext data', function (t) {
 })
 
 test('encode/decode 4 bytes fixext data', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   function MyType (data) {
     this.data = data
   }
 
   function mytypeEncode (obj) {
-    var buf = Buffer.allocUnsafe(4)
+    const buf = Buffer.allocUnsafe(4)
     buf.writeUInt32BE(obj.data, 0)
     return buf
   }
@@ -137,7 +137,7 @@ test('encode/decode 4 bytes fixext data', function (t) {
 
   all.forEach(function (orig) {
     t.test('encoding a custom obj encoded as ' + orig.data, function (t) {
-      var buf = encoder.encode(orig)
+      const buf = encoder.encode(orig)
       t.equal(buf.length, 6, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xd6, 'must have the fixext header')
       t.equal(buf.readUInt8(1), 0x44, 'must include the custom type id')
@@ -146,7 +146,7 @@ test('encode/decode 4 bytes fixext data', function (t) {
     })
 
     t.test('decoding a custom obj encoded as ' + orig.data, function (t) {
-      var buf = Buffer.allocUnsafe(6)
+      const buf = Buffer.allocUnsafe(6)
       buf[0] = 0xd6
       buf[1] = 0x44
       buf.writeUInt32BE(orig.data, 2)
@@ -165,15 +165,15 @@ test('encode/decode 4 bytes fixext data', function (t) {
 })
 
 test('encode/decode 8 bytes fixext data', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   function MyType (data) {
     this.data = data
   }
 
   function mytypeEncode (obj) {
-    var buf = Buffer.allocUnsafe(8)
+    const buf = Buffer.allocUnsafe(8)
     buf.writeUInt32BE(obj.data / 2, 0)
     buf.writeUInt32BE(obj.data / 2, 4)
     return buf
@@ -191,7 +191,7 @@ test('encode/decode 8 bytes fixext data', function (t) {
 
   all.forEach(function (orig) {
     t.test('encoding a custom obj encoded as ' + orig.data, function (t) {
-      var buf = encoder.encode(orig)
+      const buf = encoder.encode(orig)
       t.equal(buf.length, 10, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xd7, 'must have the fixext header')
       t.equal(buf.readUInt8(1), 0x44, 'must include the custom type id')
@@ -200,7 +200,7 @@ test('encode/decode 8 bytes fixext data', function (t) {
     })
 
     t.test('decoding a custom obj encoded as ' + orig.data, function (t) {
-      var buf = Buffer.allocUnsafe(10)
+      const buf = Buffer.allocUnsafe(10)
       buf[0] = 0xd7
       buf[1] = 0x44
       buf.writeUInt32BE(orig.data / 2, 2)
@@ -220,15 +220,15 @@ test('encode/decode 8 bytes fixext data', function (t) {
 })
 
 test('encode/decode 16 bytes fixext data', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   function MyType (data) {
     this.data = data
   }
 
   function mytypeEncode (obj) {
-    var buf = Buffer.allocUnsafe(16)
+    const buf = Buffer.allocUnsafe(16)
     buf.writeUInt32BE(obj.data / 4, 0)
     buf.writeUInt32BE(obj.data / 4, 4)
     buf.writeUInt32BE(obj.data / 4, 8)
@@ -248,7 +248,7 @@ test('encode/decode 16 bytes fixext data', function (t) {
 
   all.forEach(function (orig) {
     t.test('encoding a custom obj encoded as ' + orig.data, function (t) {
-      var buf = encoder.encode(orig)
+      const buf = encoder.encode(orig)
       t.equal(buf.length, 18, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xd8, 'must have the fixext header')
       t.equal(buf.readUInt8(1), 0x46, 'must include the custom type id')
@@ -257,7 +257,7 @@ test('encode/decode 16 bytes fixext data', function (t) {
     })
 
     t.test('decoding a custom obj encoded as ' + orig.data, function (t) {
-      var buf = Buffer.allocUnsafe(18)
+      const buf = Buffer.allocUnsafe(18)
       buf[0] = 0xd8
       buf[1] = 0x46
       buf.writeUInt32BE(orig.data / 4, 2)
@@ -279,15 +279,15 @@ test('encode/decode 16 bytes fixext data', function (t) {
 })
 
 test('encode/decode fixext inside a map', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   function MyType (data) {
     this.data = data
   }
 
   function mytypeEncode (obj) {
-    var buf = Buffer.allocUnsafe(4)
+    const buf = Buffer.allocUnsafe(4)
     buf.writeUInt32BE(obj.data, 0)
     return buf
   }
@@ -308,7 +308,7 @@ test('encode/decode fixext inside a map', function (t) {
 
   all.forEach(function (orig) {
     t.test('mirror test with a custom obj inside a map', function (t) {
-      var encoded = encoder.encode(orig)
+      const encoded = encoder.encode(orig)
       t.deepEqual(encoder.decode(encoded), orig, 'must stay the same')
       t.end()
     })
@@ -318,15 +318,15 @@ test('encode/decode fixext inside a map', function (t) {
 })
 
 test('encode/decode 8 bytes fixext data', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   function MyType (data) {
     this.data = data
   }
 
   function mytypeEncode (obj) {
-    var buf = Buffer.allocUnsafe(8)
+    const buf = Buffer.allocUnsafe(8)
     buf.writeUInt32BE(obj.data / 2, 0)
     buf.writeUInt32BE(obj.data / 2, 4)
     return buf
@@ -344,7 +344,7 @@ test('encode/decode 8 bytes fixext data', function (t) {
 
   all.forEach(function (orig) {
     t.test('encoding a custom obj encoded as ' + orig.data, function (t) {
-      var buf = encoder.encode(orig)
+      const buf = encoder.encode(orig)
       t.equal(buf.length, 10, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xd7, 'must have the fixext header')
       t.equal(buf.readUInt8(1), 0x44, 'must include the custom type id')
@@ -353,7 +353,7 @@ test('encode/decode 8 bytes fixext data', function (t) {
     })
 
     t.test('decoding a custom obj encoded as ' + orig.data, function (t) {
-      var buf = Buffer.allocUnsafe(10)
+      const buf = Buffer.allocUnsafe(10)
       buf[0] = 0xd7
       buf[1] = 0x44
       buf.writeUInt32BE(orig.data / 2, 2)
@@ -373,15 +373,15 @@ test('encode/decode 8 bytes fixext data', function (t) {
 })
 
 test('encode/decode 16 bytes fixext data', function (t) {
-  var encoder = msgpack()
-  var all = []
+  const encoder = msgpack()
+  const all = []
 
   function MyType (data) {
     this.data = data
   }
 
   function mytypeEncode (obj) {
-    var buf = Buffer.allocUnsafe(16)
+    const buf = Buffer.allocUnsafe(16)
     buf.writeUInt32BE(obj.data / 4, 0)
     buf.writeUInt32BE(obj.data / 4, 4)
     buf.writeUInt32BE(obj.data / 4, 8)
@@ -401,7 +401,7 @@ test('encode/decode 16 bytes fixext data', function (t) {
 
   all.forEach(function (orig) {
     t.test('encoding a custom obj encoded as ' + orig.data, function (t) {
-      var buf = encoder.encode(orig)
+      const buf = encoder.encode(orig)
       t.equal(buf.length, 18, 'must have the right length')
       t.equal(buf.readUInt8(0), 0xd8, 'must have the fixext header')
       t.equal(buf.readUInt8(1), 0x46, 'must include the custom type id')
@@ -410,7 +410,7 @@ test('encode/decode 16 bytes fixext data', function (t) {
     })
 
     t.test('decoding a custom obj encoded as ' + orig.data, function (t) {
-      var buf = Buffer.allocUnsafe(18)
+      const buf = Buffer.allocUnsafe(18)
       buf[0] = 0xd8
       buf[1] = 0x46
       buf.writeUInt32BE(orig.data / 4, 2)
@@ -429,11 +429,11 @@ test('encode/decode 16 bytes fixext data', function (t) {
   })
 
   t.test('decoding an incomplete 1 byte fixext data', function (t) {
-    var encoder = msgpack()
-    var buf = Buffer.allocUnsafe(2)
+    const encoder = msgpack()
+    let buf = Buffer.allocUnsafe(2)
     buf[0] = 0xd4
     buf = bl().append(buf)
-    var origLength = buf.length
+    const origLength = buf.length
     t.throws(function () {
       encoder.decode(buf)
     }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
@@ -442,11 +442,11 @@ test('encode/decode 16 bytes fixext data', function (t) {
   })
 
   t.test('decoding an incomplete 2 byte fixext data', function (t) {
-    var encoder = msgpack()
-    var buf = Buffer.allocUnsafe(3)
+    const encoder = msgpack()
+    let buf = Buffer.allocUnsafe(3)
     buf[0] = 0xd5
     buf = bl().append(buf)
-    var origLength = buf.length
+    const origLength = buf.length
     t.throws(function () {
       encoder.decode(buf)
     }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
@@ -455,11 +455,11 @@ test('encode/decode 16 bytes fixext data', function (t) {
   })
 
   t.test('decoding an incomplete 4 byte fixext data', function (t) {
-    var encoder = msgpack()
-    var buf = Buffer.allocUnsafe(5)
+    const encoder = msgpack()
+    let buf = Buffer.allocUnsafe(5)
     buf[0] = 0xd6
     buf = bl().append(buf)
-    var origLength = buf.length
+    const origLength = buf.length
     t.throws(function () {
       encoder.decode(buf)
     }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
@@ -468,11 +468,11 @@ test('encode/decode 16 bytes fixext data', function (t) {
   })
 
   t.test('decoding an incomplete 8 byte fixext data', function (t) {
-    var encoder = msgpack()
-    var buf = Buffer.allocUnsafe(9)
+    const encoder = msgpack()
+    let buf = Buffer.allocUnsafe(9)
     buf[0] = 0xd7
     buf = bl().append(buf)
-    var origLength = buf.length
+    const origLength = buf.length
     t.throws(function () {
       encoder.decode(buf)
     }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
@@ -481,11 +481,11 @@ test('encode/decode 16 bytes fixext data', function (t) {
   })
 
   t.test('decoding an incomplete 16 byte fixext data', function (t) {
-    var encoder = msgpack()
-    var buf = Buffer.allocUnsafe(17)
+    const encoder = msgpack()
+    let buf = Buffer.allocUnsafe(17)
     buf[0] = 0xd8
     buf = bl().append(buf)
-    var origLength = buf.length
+    const origLength = buf.length
     t.throws(function () {
       encoder.decode(buf)
     }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/floats.js b/test/floats.js
index 8c0a132..540a3fb 100644
--- a/test/floats.js
+++ b/test/floats.js
@@ -1,19 +1,19 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 test('encoding/decoding 32-bits float numbers', function (t) {
-  var encoder = msgpack()
-  var float32 = [
+  const encoder = msgpack()
+  const float32 = [
     1.5,
     0.15625,
     -2.5
   ]
 
-  var float64 = [
+  const float64 = [
     Math.pow(2, 150),
     1.337,
     2.2
@@ -21,28 +21,27 @@ test('encoding/decoding 32-bits float numbers', function (t) {
 
   float64.forEach(function (num) {
     t.test('encoding ' + num, function (t) {
-      var buf = encoder.encode(num)
+      const buf = encoder.encode(num)
       t.equal(buf.length, 9, 'must have 5 bytes')
       t.equal(buf[0], 0xcb, 'must have the proper header')
 
-      var dec = buf.readDoubleBE(1)
+      const dec = buf.readDoubleBE(1)
       t.equal(dec, num, 'must decode correctly')
       t.end()
     })
 
     t.test('decoding ' + num, function (t) {
-      var buf = Buffer.allocUnsafe(9)
-      var dec
+      const buf = Buffer.allocUnsafe(9)
       buf[0] = 0xcb
       buf.writeDoubleBE(num, 1)
 
-      dec = encoder.decode(buf)
+      const dec = encoder.decode(buf)
       t.equal(dec, num, 'must decode correctly')
       t.end()
     })
 
     t.test('mirror test ' + num, function (t) {
-      var dec = encoder.decode(encoder.encode(num))
+      const dec = encoder.decode(encoder.encode(num))
       t.equal(dec, num, 'must decode correctly')
       t.end()
     })
@@ -50,40 +49,39 @@ test('encoding/decoding 32-bits float numbers', function (t) {
 
   float32.forEach(function (num) {
     t.test('encoding ' + num, function (t) {
-      var buf = encoder.encode(num)
+      const buf = encoder.encode(num)
       t.equal(buf.length, 5, 'must have 5 bytes')
       t.equal(buf[0], 0xca, 'must have the proper header')
 
-      var dec = buf.readFloatBE(1)
+      const dec = buf.readFloatBE(1)
       t.equal(dec, num, 'must decode correctly')
       t.end()
     })
 
     t.test('forceFloat64 encoding ' + num, function (t) {
-      var enc = msgpack({ forceFloat64: true })
-      var buf = enc.encode(num)
+      const enc = msgpack({ forceFloat64: true })
+      const buf = enc.encode(num)
 
       t.equal(buf.length, 9, 'must have 9 bytes')
       t.equal(buf[0], 0xcb, 'must have the proper header')
 
-      var dec = buf.readDoubleBE(1)
+      const dec = buf.readDoubleBE(1)
       t.equal(dec, num, 'must decode correctly')
       t.end()
     })
 
     t.test('decoding ' + num, function (t) {
-      var buf = Buffer.allocUnsafe(5)
-      var dec
+      const buf = Buffer.allocUnsafe(5)
       buf[0] = 0xca
       buf.writeFloatBE(num, 1)
 
-      dec = encoder.decode(buf)
+      const dec = encoder.decode(buf)
       t.equal(dec, num, 'must decode correctly')
       t.end()
     })
 
     t.test('mirror test ' + num, function (t) {
-      var dec = encoder.decode(encoder.encode(num))
+      const dec = encoder.decode(encoder.encode(num))
       t.equal(dec, num, 'must decode correctly')
       t.end()
     })
@@ -93,11 +91,11 @@ test('encoding/decoding 32-bits float numbers', function (t) {
 })
 
 test('decoding an incomplete 32-bits float numbers', function (t) {
-  var encoder = msgpack()
-  var buf = Buffer.allocUnsafe(4)
+  const encoder = msgpack()
+  let buf = Buffer.allocUnsafe(4)
   buf[0] = 0xca
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
@@ -106,11 +104,11 @@ test('decoding an incomplete 32-bits float numbers', function (t) {
 })
 
 test('decoding an incomplete 64-bits float numbers', function (t) {
-  var encoder = msgpack()
-  var buf = Buffer.allocUnsafe(8)
+  const encoder = msgpack()
+  let buf = Buffer.allocUnsafe(8)
   buf[0] = 0xcb
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     encoder.decode(buf)
   }, encoder.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/functions.js b/test/functions.js
index 66a7030..4a50103 100644
--- a/test/functions.js
+++ b/test/functions.js
@@ -1,15 +1,15 @@
 'use strict'
 
-var test = require('tape').test
-var msgpack = require('../')
-var noop = function () {}
+const test = require('tape').test
+const msgpack = require('../')
+const noop = function () {}
 
 test('encode a function inside a map', function (t) {
-  var encoder = msgpack()
-  var expected = {
+  const encoder = msgpack()
+  const expected = {
     hello: 'world'
   }
-  var toEncode = {
+  const toEncode = {
     hello: 'world',
     func: noop
   }
diff --git a/test/levelup-encoding.js b/test/levelup-encoding.js
index 19b43b2..6bcab77 100644
--- a/test/levelup-encoding.js
+++ b/test/levelup-encoding.js
@@ -1,17 +1,17 @@
 'use strict'
 
-var test = require('tape').test
-var level = require('memdb')
-var msgpack = require('../')
+const test = require('tape').test
+const level = require('memdb')
+const msgpack = require('../')
 
 test('msgpack level encoding put', function (t) {
   t.plan(4)
 
-  var pack = msgpack()
-  var db = level({
+  const pack = msgpack()
+  const db = level({
     valueEncoding: pack
   })
-  var obj = { my: 'obj' }
+  const obj = { my: 'obj' }
 
   db.put('hello', obj, function (err) {
     t.error(err, 'put has no errors')
@@ -28,12 +28,12 @@ test('msgpack level encoding put', function (t) {
 test('msgpack level encoding get', function (t) {
   t.plan(4)
 
-  var pack = msgpack()
-  var db = level({
+  const pack = msgpack()
+  const db = level({
     valueEncoding: pack
   })
-  var obj = { my: 'obj' }
-  var buf = pack.encode(obj)
+  const obj = { my: 'obj' }
+  const buf = pack.encode(obj)
 
   db.put('hello', buf, { valueEncoding: 'binary' }, function (err) {
     t.error(err, 'putting has no errors')
@@ -50,11 +50,11 @@ test('msgpack level encoding get', function (t) {
 test('msgpack level encoding mirror', function (t) {
   t.plan(4)
 
-  var pack = msgpack()
-  var db = level({
+  const pack = msgpack()
+  const db = level({
     valueEncoding: pack
   })
-  var obj = { my: 'obj' }
+  const obj = { my: 'obj' }
 
   db.put('hello', obj, function (err) {
     t.error(err, 'putting has no errors')
diff --git a/test/map-with-object-key.js b/test/map-with-object-key.js
index cb0329d..ad7c48e 100644
--- a/test/map-with-object-key.js
+++ b/test/map-with-object-key.js
@@ -1,8 +1,8 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
 
 test('encode/decode map with multiple short buffers as both keys and values', function (t) {
   const first = Buffer.from('first')
@@ -13,13 +13,13 @@ test('encode/decode map with multiple short buffers as both keys and values', fu
     .set(second, third)
     .set(third, first)
 
-  var pack = msgpack()
+  const pack = msgpack()
 
   const newMapping = pack.decode(pack.encode(mapping))
 
   t.equals(newMapping.size, mapping.size)
-  t.deepEqual([ ...newMapping.keys() ], [ ...mapping.keys() ])
-  t.deepEqual([ ...newMapping.values() ], [ ...mapping.values() ])
+  t.deepEqual([...newMapping.keys()], [...mapping.keys()])
+  t.deepEqual([...newMapping.values()], [...mapping.values()])
 
   t.end()
 })
diff --git a/test/null.js b/test/null.js
index 0407424..4e4de06 100644
--- a/test/null.js
+++ b/test/null.js
@@ -1,11 +1,11 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
 
 test('encode/decode null', function (t) {
-  var encoder = msgpack()
+  const encoder = msgpack()
 
   t.equal(encoder.encode(null)[0], 0xc0, 'encode null as 0xc0')
   t.equal(encoder.encode(null).length, 1, 'encode a buffer of length 1')
diff --git a/test/numerictypeasserts.js b/test/numerictypeasserts.js
index 3b523a7..098e0d1 100644
--- a/test/numerictypeasserts.js
+++ b/test/numerictypeasserts.js
@@ -1,10 +1,10 @@
 'use strict'
 
-var test = require('tape').test
-var msgpack = require('../')
+const test = require('tape').test
+const msgpack = require('../')
 
 test('custom type registeration assertions', function (t) {
-  var encoder = msgpack()
+  const encoder = msgpack()
 
   function Type0 (value) {
     this.value = value
@@ -37,8 +37,8 @@ test('custom type registeration assertions', function (t) {
     encoder.register(-1, TypeNeg, typeNegEncode, typeNegDecode)
   }, undefined, 'A type registered as a negative value should throw')
 
-  var encoded = encoder.encode(new Type0('hi'))
-  var decoded
+  const encoded = encoder.encode(new Type0('hi'))
+  let decoded
   t.equal(encoded.readUInt8(1), 0x0, 'must use the custom type assigned')
   t.doesNotThrow(function () {
     decoded = encoder.decode(encoded)
diff --git a/test/object-prototype-poisoning.js b/test/object-prototype-poisoning.js
index 18644cd..641b25f 100644
--- a/test/object-prototype-poisoning.js
+++ b/test/object-prototype-poisoning.js
@@ -1,7 +1,7 @@
 'use strict'
 
-var test = require('tape').test
-var msgpack = require('../')
+const test = require('tape').test
+const msgpack = require('../')
 
 test('decode throws when object has forbidden __proto__ property', function (t) {
   const encoder = msgpack()
diff --git a/test/object-with-arrays.js b/test/object-with-arrays.js
index 8e93c49..d2aa429 100644
--- a/test/object-with-arrays.js
+++ b/test/object-with-arrays.js
@@ -1,12 +1,12 @@
 'use strict'
 
-var test = require('tape').test
-var msgpack = require('../')
-var bl = require('bl')
+const test = require('tape').test
+const msgpack = require('../')
+const bl = require('bl')
 
 function build (size) {
-  var array = []
-  var i
+  const array = []
+  let i
 
   for (i = 0; i < size; i++) {
     array.push(42)
@@ -16,30 +16,30 @@ function build (size) {
 }
 
 test('decoding a map with multiple big arrays', function (t) {
-  var map = {
+  const map = {
     first: build(0xffff + 42),
     second: build(0xffff + 42)
   }
-  var pack = msgpack()
+  const pack = msgpack()
 
   t.deepEqual(pack.decode(pack.encode(map)), map)
   t.end()
 })
 
 test('decoding a map with multiple big arrays. First one is incomplete', function (t) {
-  var array = build(0xffff + 42)
-  var map = {
+  const array = build(0xffff + 42)
+  const map = {
     first: array,
     second: build(0xffff + 42)
   }
-  var pack = msgpack()
+  const pack = msgpack()
 
-  var buf = pack.encode(map)
+  let buf = pack.encode(map)
   // 1 (fixmap's header 0x82) + first key's length + 1 (first array's 0xdd)
-  var sizePosOfFirstArray = 1 + pack.encode('first').length + 1
+  const sizePosOfFirstArray = 1 + pack.encode('first').length + 1
   buf.writeUInt32BE(array.length + 10, sizePosOfFirstArray) // set first array's size bigger than its actual size
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     pack.decode(buf)
   }, pack.IncompleteBufferError, 'must throw IncompleteBufferError')
@@ -48,19 +48,19 @@ test('decoding a map with multiple big arrays. First one is incomplete', functio
 })
 
 test('decoding a map with multiple big arrays. Second one is incomplete', function (t) {
-  var array = build(0xffff + 42)
-  var map = {
+  const array = build(0xffff + 42)
+  const map = {
     first: array,
     second: build(0xffff + 42)
   }
-  var pack = msgpack()
+  const pack = msgpack()
 
-  var buf = pack.encode(map)
+  let buf = pack.encode(map)
   // 1 (fixmap's header 0x82) + first key-value pair's length + second key's length + 1 (second array's 0xdd)
-  var sizePosOfSecondArray = 1 + pack.encode('first').length + pack.encode(array).length + pack.encode('second').length + 1
+  const sizePosOfSecondArray = 1 + pack.encode('first').length + pack.encode(array).length + pack.encode('second').length + 1
   buf.writeUInt32BE(array.length + 10, sizePosOfSecondArray) // set second array's size bigger than its actual size
   buf = bl().append(buf)
-  var origLength = buf.length
+  const origLength = buf.length
   t.throws(function () {
     pack.decode(buf)
   }, pack.IncompleteBufferError, 'must throw IncompleteBufferError')
diff --git a/test/object-with-buffers.js b/test/object-with-buffers.js
index 6a73136..d1a3a60 100644
--- a/test/object-with-buffers.js
+++ b/test/object-with-buffers.js
@@ -1,18 +1,18 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var fs = require('fs')
-var p = require('path')
-var msgpack = require('../')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const fs = require('fs')
+const p = require('path')
+const msgpack = require('../')
 
 test('encode/decode map with multiple short buffers', function (t) {
-  var map = {
+  const map = {
     first: Buffer.from('first'),
     second: Buffer.from('second'),
     third: Buffer.from('third')
   }
-  var pack = msgpack()
+  const pack = msgpack()
 
   t.deepEqual(pack.decode(pack.encode(map)), map)
   t.end()
@@ -20,12 +20,12 @@ test('encode/decode map with multiple short buffers', function (t) {
 
 if (process.title !== 'browser') {
   test('encode/decode map with all files in this directory', function (t) {
-    var files = fs.readdirSync(__dirname)
-    var map = files.reduce(function (acc, file) {
+    const files = fs.readdirSync(__dirname)
+    const map = files.reduce(function (acc, file) {
       acc[file] = fs.readFileSync(p.join(__dirname, file))
       return acc
     }, {})
-    var pack = msgpack()
+    const pack = msgpack()
 
     t.deepEqual(pack.decode(pack.encode(map)), map)
     t.end()
diff --git a/test/object-with-many-keys.js b/test/object-with-many-keys.js
index 1cbfc33..d7dc05f 100644
--- a/test/object-with-many-keys.js
+++ b/test/object-with-many-keys.js
@@ -1,18 +1,18 @@
 'use strict'
 
-var test = require('tape').test
-var msgpack = require('../')
+const test = require('tape').test
+const msgpack = require('../')
 
 test('encode/decode map with 10 keys', function (t) {
-  var map = {}
+  const map = {}
 
-  for (var i = 0; i < 10; i++) {
+  for (let i = 0; i < 10; i++) {
     map[i] = i
   }
 
-  var pack = msgpack()
+  const pack = msgpack()
 
-  var encoded = pack.encode(map)
+  const encoded = pack.encode(map)
 
   // map16 byte
   t.equal(encoded[0], 0x8A)
@@ -22,15 +22,15 @@ test('encode/decode map with 10 keys', function (t) {
 })
 
 test('encode/decode map with 10000 keys', function (t) {
-  var map = {}
+  const map = {}
 
-  for (var i = 0; i < 10000; i++) {
+  for (let i = 0; i < 10000; i++) {
     map[i] = i
   }
 
-  var pack = msgpack()
+  const pack = msgpack()
 
-  var encoded = pack.encode(map)
+  const encoded = pack.encode(map)
 
   // map16 byte
   t.equal(encoded[0], 0xde)
@@ -40,15 +40,15 @@ test('encode/decode map with 10000 keys', function (t) {
 })
 
 test('encode/decode map with 100000 keys', function (t) {
-  var map = {}
+  const map = {}
 
-  for (var i = 0; i < 100000; i++) {
+  for (let i = 0; i < 100000; i++) {
     map[i] = i
   }
 
-  var pack = msgpack()
+  const pack = msgpack()
 
-  var encoded = pack.encode(map)
+  const encoded = pack.encode(map)
 
   // map32 byte
   t.equal(encoded[0], 0xdf)
@@ -58,13 +58,13 @@ test('encode/decode map with 100000 keys', function (t) {
 })
 
 test('encode/decode map with 1000000 keys', function (t) {
-  var map = {}
+  const map = {}
 
-  for (var i = 0; i < 1000000; i++) {
+  for (let i = 0; i < 1000000; i++) {
     map[i] = i
   }
 
-  var pack = msgpack()
+  const pack = msgpack()
 
   t.deepEqual(pack.decode(pack.encode(map)), map)
   t.end()
diff --git a/test/object-with-strings.js b/test/object-with-strings.js
index 709456f..e17f3fd 100644
--- a/test/object-with-strings.js
+++ b/test/object-with-strings.js
@@ -1,17 +1,17 @@
 'use strict'
 
-var test = require('tape').test
-var fs = require('fs')
-var p = require('path')
-var msgpack = require('../')
+const test = require('tape').test
+const fs = require('fs')
+const p = require('path')
+const msgpack = require('../')
 
 test('encode/decode map with multiple short buffers', function (t) {
-  var map = {
+  const map = {
     first: 'first',
     second: 'second',
     third: 'third'
   }
-  var pack = msgpack()
+  const pack = msgpack()
 
   t.deepEqual(pack.decode(pack.encode(map)), map)
   t.end()
@@ -19,12 +19,12 @@ test('encode/decode map with multiple short buffers', function (t) {
 
 if (process.title !== 'browser') {
   test('encode/decode map with all files in this directory', function (t) {
-    var files = fs.readdirSync(__dirname)
-    var map = files.reduce(function (acc, file) {
+    const files = fs.readdirSync(__dirname)
+    const map = files.reduce(function (acc, file) {
       acc[file] = fs.readFileSync(p.join(__dirname, file)).toString('utf8')
       return acc
     }, {})
-    var pack = msgpack()
+    const pack = msgpack()
 
     t.deepEqual(pack.decode(pack.encode(map)), map)
     t.end()
diff --git a/test/prefer-map.js b/test/prefer-map.js
index 0d56fa3..d975687 100644
--- a/test/prefer-map.js
+++ b/test/prefer-map.js
@@ -9,7 +9,7 @@ const map = new Map()
   .set('01', null)
 
 test('round-trip string-keyed Maps', function (t) {
-  const encoder = msgpack({preferMap: true})
+  const encoder = msgpack({ preferMap: true })
 
   for (const input of [new Map(), map]) {
     const result = encoder.decode(encoder.encode(input))
@@ -21,7 +21,7 @@ test('round-trip string-keyed Maps', function (t) {
 })
 
 test('preserve iteration order of string-keyed Maps', function (t) {
-  const encoder = msgpack({preferMap: true})
+  const encoder = msgpack({ preferMap: true })
   const decoded = encoder.decode(encoder.encode(map))
 
   t.deepEqual([...decoded.keys()], [...map.keys()])
@@ -30,7 +30,7 @@ test('preserve iteration order of string-keyed Maps', function (t) {
 })
 
 test('user can still encode objects as ext maps', function (t) {
-  const encoder = msgpack({preferMap: true})
+  const encoder = msgpack({ preferMap: true })
   const tag = 0x42
 
   // Polyfill Object.fromEntries for node 10
@@ -52,10 +52,10 @@ test('user can still encode objects as ext maps', function (t) {
   const inputs = [
     {},
     new Map(),
-    {foo: 'bar'},
+    { foo: 'bar' },
     new Map().set('foo', 'bar'),
     new Map().set(null, null),
-    {0: 'baz'},
+    { 0: 'baz' },
     ['baz']
   ]
 
diff --git a/test/streams.js b/test/streams.js
index 77b722f..f22c9bc 100644
--- a/test/streams.js
+++ b/test/streams.js
@@ -1,17 +1,17 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
-var BufferList = require('bl')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
+const BufferList = require('bl')
 
 test('must send an object through', function (t) {
   t.plan(1)
 
-  var pack = msgpack()
-  var encoder = pack.encoder()
-  var decoder = pack.decoder()
-  var data = { hello: 'world' }
+  const pack = msgpack()
+  const encoder = pack.encoder()
+  const decoder = pack.decoder()
+  const data = { hello: 'world' }
 
   encoder.pipe(decoder)
 
@@ -23,10 +23,10 @@ test('must send an object through', function (t) {
 })
 
 test('must send three objects through', function (t) {
-  var pack = msgpack()
-  var encoder = pack.encoder()
-  var decoder = pack.decoder()
-  var data = [
+  const pack = msgpack()
+  const encoder = pack.encoder()
+  const decoder = pack.decoder()
+  const data = [
     { hello: 1 },
     { hello: 2 },
     { hello: 3 }
@@ -46,10 +46,10 @@ test('must send three objects through', function (t) {
 })
 
 test('end-to-end', function (t) {
-  var pack = msgpack()
-  var encoder = pack.encoder()
-  var decoder = pack.decoder()
-  var data = [
+  const pack = msgpack()
+  const encoder = pack.encoder()
+  const decoder = pack.decoder()
+  const data = [
     { hello: 1 },
     { hello: 2 },
     { hello: 3 }
@@ -71,9 +71,9 @@ test('end-to-end', function (t) {
 test('encoding error wrapped', function (t) {
   t.plan(1)
 
-  var pack = msgpack()
-  var encoder = pack.encoder()
-  var data = new MyType()
+  const pack = msgpack()
+  const encoder = pack.encoder()
+  const data = new MyType()
 
   function MyType () {
   }
@@ -97,10 +97,10 @@ test('encoding error wrapped', function (t) {
 test('decoding error wrapped', function (t) {
   t.plan(1)
 
-  var pack = msgpack()
-  var encoder = pack.encoder()
-  var decoder = pack.decoder()
-  var data = new MyType()
+  const pack = msgpack()
+  const encoder = pack.encoder()
+  const decoder = pack.decoder()
+  const data = new MyType()
 
   function MyType () {
   }
@@ -127,10 +127,10 @@ test('decoding error wrapped', function (t) {
 test('decoding error wrapped', function (t) {
   t.plan(1)
 
-  var pack = msgpack()
-  var encoder = pack.encoder({ header: false })
-  var decoder = pack.decoder({ header: false })
-  var data = new MyType()
+  const pack = msgpack()
+  const encoder = pack.encoder({ header: false })
+  const decoder = pack.decoder({ header: false })
+  const data = new MyType()
 
   function MyType () {
   }
@@ -155,10 +155,10 @@ test('decoding error wrapped', function (t) {
 })
 
 test('concatenated buffers work', function (t) {
-  var pack = msgpack()
-  var encoder = pack.encoder()
-  var decoder = pack.decoder()
-  var data = [
+  const pack = msgpack()
+  const encoder = pack.encoder()
+  const decoder = pack.decoder()
+  const data = [
     { hello: 1 },
     { hello: 2 },
     { hello: 3 }
@@ -166,7 +166,7 @@ test('concatenated buffers work', function (t) {
 
   t.plan(data.length)
 
-  var bl = new BufferList()
+  const bl = new BufferList()
   encoder.on('data', bl.append.bind(bl))
 
   data.forEach(encoder.write.bind(encoder))
@@ -176,7 +176,7 @@ test('concatenated buffers work', function (t) {
   })
 
   encoder.once('finish', function () {
-    var buf = bl.slice()
+    const buf = bl.slice()
     decoder.write(buf)
   })
 
@@ -186,9 +186,9 @@ test('concatenated buffers work', function (t) {
 test('nil processing works', function (t) {
   t.plan(3)
 
-  var pack = msgpack()
-  var decoder = pack.decoder({wrap: true})
-  var decodedItemIndex = 0
+  const pack = msgpack()
+  const decoder = pack.decoder({ wrap: true })
+  let decodedItemIndex = 0
 
   decoder.on('data', function (chunk) {
     decodedItemIndex++
@@ -206,11 +206,11 @@ test('nil processing works', function (t) {
 test('encoder wrap mode works', function (t) {
   t.plan(1)
 
-  var pack = msgpack()
-  var encoder = pack.encoder({wrap: true})
-  var decoder = pack.decoder()
-  var data = { hello: 'world' }
-  var wrappedData = {value: data}
+  const pack = msgpack()
+  const encoder = pack.encoder({ wrap: true })
+  const decoder = pack.decoder()
+  const data = { hello: 'world' }
+  const wrappedData = { value: data }
 
   encoder.pipe(decoder)
 
@@ -224,10 +224,10 @@ test('encoder wrap mode works', function (t) {
 test('encoder/decoder wrap mode must send an object through', function (t) {
   t.plan(1)
 
-  var pack = msgpack()
-  var encoder = pack.encoder({wrap: true})
-  var decoder = pack.decoder({wrap: true})
-  var data = {value: { hello: 'world' }}
+  const pack = msgpack()
+  const encoder = pack.encoder({ wrap: true })
+  const decoder = pack.decoder({ wrap: true })
+  const data = { value: { hello: 'world' } }
 
   encoder.pipe(decoder)
 
@@ -240,13 +240,13 @@ test('encoder/decoder wrap mode must send an object through', function (t) {
 
 test('encoder pack null', function (t) {
   t.plan(2)
-  var pack = msgpack()
-  var encoder = pack.encoder({wrap: true})
-  var decoder = pack.decoder({wrap: true})
+  const pack = msgpack()
+  const encoder = pack.encoder({ wrap: true })
+  const decoder = pack.decoder({ wrap: true })
 
   encoder.pipe(decoder)
 
-  var decodedItemIndex = 0
+  let decodedItemIndex = 0
   decoder.on('data', function (chunk) {
     decodedItemIndex++
     t.deepEqual(chunk.value, null)
@@ -256,6 +256,6 @@ test('encoder pack null', function (t) {
     t.equal(decodedItemIndex, 1)
   })
 
-  encoder.write({value: null})
+  encoder.write({ value: null })
   encoder.end()
 })
diff --git a/test/timestamps.js b/test/timestamps.js
index 61dad03..aae5b5d 100644
--- a/test/timestamps.js
+++ b/test/timestamps.js
@@ -1,21 +1,21 @@
 'use strict'
 
-var Buffer = require('safe-buffer').Buffer
-var test = require('tape').test
-var msgpack = require('../')
+const Buffer = require('safe-buffer').Buffer
+const test = require('tape').test
+const msgpack = require('../')
 
 test('timestamp disabling', function (t) {
-  var encoder = msgpack({disableTimestampEncoding: true})
-  var timestamps = [
+  const encoder = msgpack({ disableTimestampEncoding: true })
+  const timestamps = [
     [new Date('2018-01-02T03:04:05.000000000Z'), [0x80]]
   ]
 
   timestamps.forEach(function (testcase) {
-    var item = testcase[0]
-    var expected = testcase[1]
+    const item = testcase[0]
+    const expected = testcase[1]
 
     t.test('encoding ' + item.toString(), function (t) {
-      var buf = encoder.encode(item).slice()
+      const buf = encoder.encode(item).slice()
       t.equal(buf.length, expected.length, 'must have ' + expected.length + ' bytes')
       t.equal(buf[0], expected[0], 'Should return 0x80 ({}) by default')
       t.end()
@@ -25,8 +25,8 @@ test('timestamp disabling', function (t) {
   t.end()
 })
 test('encoding/decoding timestamp 64', function (t) {
-  var encoder = msgpack()
-  var timestamps = [
+  const encoder = msgpack()
+  const timestamps = [
     [new Date('2018-01-02T03:04:05.000000000Z'), [0xd6, 0xff, 0x5a, 0x4a, 0xf6, 0xa5]],
     [new Date('2038-01-19T03:14:08.000000000Z'), [0xd6, 0xff, 0x80, 0x00, 0x00, 0x00]],
     [new Date('2038-01-19T03:14:07.999000000Z'), [0xd7, 0xff, 0xee, 0x2E, 0x1F, 0x00, 0x7f, 0xff, 0xff, 0xff]],
@@ -35,11 +35,11 @@ test('encoding/decoding timestamp 64', function (t) {
   ]
 
   timestamps.forEach(function (testcase) {
-    var item = testcase[0]
-    var expected = testcase[1]
+    const item = testcase[0]
+    const expected = testcase[1]
 
     t.test('encoding ' + item.toString(), function (t) {
-      var buf = encoder.encode(item).slice()
+      const buf = encoder.encode(item).slice()
       t.equal(buf.length, expected.length, 'must have ' + expected.length + ' bytes')
       switch (expected.length) {
         case 6:
@@ -50,15 +50,15 @@ test('encoding/decoding timestamp 64', function (t) {
           break
       }
       t.equal(buf.readInt8(1), -1, 'must have the correct type') // Signed
-      for (var j = 2; j < buf.length; j++) {
+      for (let j = 2; j < buf.length; j++) {
         t.equal(buf[j], expected[j], 'byte ' + (j - 2) + ' match')
       }
       t.end()
     })
 
     t.test('decoding ' + item, function (t) {
-      var buf = Buffer.from(expected)
-      var dt = encoder.decode(buf)
+      const buf = Buffer.from(expected)
+      const dt = encoder.decode(buf)
       t.equal(dt.toString(), item.toString(), 'must decode correctly\nDecoded:\t' + dt * 1 + '\nExp:\t' + item * 1)
       t.end()
     })
@@ -73,8 +73,8 @@ test('encoding/decoding timestamp 64', function (t) {
 })
 
 test('encoding/decoding timestamp 96', function (t) {
-  var encoder = msgpack()
-  var timestamps = [
+  const encoder = msgpack()
+  const timestamps = [
     [new Date('0001-01-02T03:04:05.000000000Z'), [0xc7, 0x0c, 0xff, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xf1, 0x88, 0x6f, 0x85, 0xa5]],
     [new Date('1251-01-19T03:14:08.000000000Z'), [0xc7, 0x0c, 0xff, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xfa, 0xb7, 0xb2, 0xdf, 0x00]],
     [new Date('1526-01-19T03:14:07.999000000Z'), [0xc7, 0x0c, 0xff, 0x3b, 0x8b, 0x87, 0xc0, 0xff, 0xff, 0xff, 0xfc, 0xbc, 0xf4, 0x34, 0x7f]],
@@ -84,24 +84,24 @@ test('encoding/decoding timestamp 96', function (t) {
   ]
 
   timestamps.forEach(function (testcase) {
-    var item = testcase[0]
-    var expected = testcase[1]
+    const item = testcase[0]
+    const expected = testcase[1]
 
     t.test('encoding ' + item.toString(), function (t) {
-      var buf = encoder.encode(item).slice()
+      const buf = encoder.encode(item).slice()
       t.equal(buf.length, expected.length, 'must have ' + expected.length + ' bytes')
       t.equal(buf[0], 0xc7, 'must have the correct header')
       t.equal(buf.readInt8(1), 12, 'must have the correct size')
       t.equal(buf.readInt8(2), -1, 'must have the correct type') // Signed
-      for (var j = 3; j < buf.length; j++) {
+      for (let j = 3; j < buf.length; j++) {
         t.equal(buf[j], expected[j], 'byte ' + (j - 3) + ' match')
       }
       t.end()
     })
 
     t.test('decoding ' + item, function (t) {
-      var buf = Buffer.from(expected)
-      var dt = encoder.decode(buf)
+      const buf = Buffer.from(expected)
+      const dt = encoder.decode(buf)
       t.equal(dt.toString(), item.toString(), 'must decode correctly\nDecoded:\t' + dt * 1 + '\nExp:\t' + item * 1)
       t.end()
     })