added transaction support for autorun method

benchmark-results.md

@@ -1,6 +1,6 @@
-mobX create observable, autorun and dispose x 39,205 ops/sec ±5.73% (71 runs sampled)
+mobX create observable, autorun and dispose x 40,866 ops/sec ±3.94% (75 runs sampled)
 
-proxevable create observable, autorun and dispose x 76,322 ops/sec ±5.73% (73 runs sampled)
+proxevable create observable, autorun and dispose x 75,569 ops/sec ±5.37% (72 runs sampled)
 
 Fastest is proxevable create observable, autorun and dispose
 

index.js

@@ -4,6 +4,16 @@ const subscriptions = new WeakMap()
 
 const _ = require('lodash')
 let autorunFn = null
+const transactionStack = []
+const autorunsAfterTransaction = new Set()
+
+const transactionallyCall = (cb) => {
+  if (transactionStack.length > 0) {
+    autorunsAfterTransaction.add(cb)
+  } else {
+    cb()
+  }
+}
 
 const api = {
   observable: (source) => {
@@ -50,7 +60,7 @@ const api = {
           if (thisSubscriptions[sKey]) {
             thisSubscriptions[sKey].forEach((callback) => {
               autorunFn = callback
-              callback()
+              transactionallyCall(callback)
             })
           }
           autorunFn = null
@@ -111,6 +121,16 @@ const api = {
     return () => {
       fn.$onDispose.forEach((cb) => cb())
     }
+  },
+  transaction: (fn) => {
+    fn.toBeCalledAfter = new Set()
+    transactionStack.push(fn)
+    fn()
+    if (fn === transactionStack[0]) {
+      autorunsAfterTransaction.forEach((cb) => {
+        cb()
+      })
+    }
   }
 }
 

test/transaction.spec.js

@@ -0,0 +1,20 @@
+import test from 'ava'
+import {observable, autorun, transaction} from '../index'
+
+test('transaction batches', t => {
+  let c = 0
+  const a = observable({g: 0})
+  autorun(() => {
+    const ident = (v) => v
+    ident(a.g)
+    c += 1
+  })
+  transaction(() => {
+    a.g = 1
+    transaction(() => {
+      a.g = 2
+      a.g = 3
+    })
+  })
+  t.truthy(c === 2)
+})