refactor: Port module to TS, Jest, ESLint (#7)

BREAKING: The main export is now a `default` export.

.eslintignore

@@ -0,0 +1,3 @@
+node_modules/
+coverage/
+lib/

.eslintrc.json

@@ -0,0 +1,62 @@
+{
+    "extends": ["eslint:recommended", "prettier"],
+    "env": {
+        "node": true,
+        "es6": true
+    },
+    "rules": {
+        "eqeqeq": [2, "smart"],
+        "no-caller": 2,
+        "dot-notation": 2,
+        "no-var": 2,
+        "prefer-const": 2,
+        "prefer-arrow-callback": [2, { "allowNamedFunctions": true }],
+        "arrow-body-style": [2, "as-needed"],
+        "object-shorthand": 2,
+        "prefer-template": 2,
+        "one-var": [2, "never"],
+        "prefer-destructuring": [2, { "object": true }],
+        "capitalized-comments": 2,
+        "multiline-comment-style": [2, "starred-block"],
+        "spaced-comment": 2,
+        "yoda": [2, "never"],
+        "curly": [2, "multi-line"],
+        "no-else-return": 2
+    },
+    "overrides": [
+        {
+            "files": "*.ts",
+            "extends": [
+                "plugin:@typescript-eslint/eslint-recommended",
+                "plugin:@typescript-eslint/recommended",
+                "prettier/@typescript-eslint"
+            ],
+            "parserOptions": {
+                "sourceType": "module",
+                "project": "./tsconfig.eslint.json"
+            },
+            "rules": {
+                "@typescript-eslint/prefer-for-of": 0,
+                "@typescript-eslint/member-ordering": 0,
+                "@typescript-eslint/explicit-function-return-type": 0,
+                "@typescript-eslint/no-unused-vars": 0,
+                "@typescript-eslint/no-use-before-define": [
+                    2,
+                    { "functions": false }
+                ],
+                "@typescript-eslint/consistent-type-definitions": [
+                    2,
+                    "interface"
+                ],
+                "@typescript-eslint/prefer-function-type": 2,
+                "@typescript-eslint/no-unnecessary-type-arguments": 2,
+                "@typescript-eslint/prefer-string-starts-ends-with": 2,
+                "@typescript-eslint/prefer-readonly": 2,
+                "@typescript-eslint/prefer-includes": 2,
+                "@typescript-eslint/no-unnecessary-condition": 2,
+                "@typescript-eslint/switch-exhaustiveness-check": 2,
+                "@typescript-eslint/prefer-nullish-coalescing": 2
+            }
+        }
+    ]
+}

.github/FUNDING.yml

@@ -1,12 +1,2 @@
-# These are supported funding model platforms
-
-github: # Replace with up to 4 GitHub Sponsors-enabled usernames e.g., [user1, user2]
-patreon: # Replace with a single Patreon username
-open_collective: # Replace with a single Open Collective username
-ko_fi: # Replace with a single Ko-fi username
+github: [fb55]
 tidelift: "npm/nth-check"
-community_bridge: # Replace with a single Community Bridge project-name e.g., cloud-foundry
-liberapay: # Replace with a single Liberapay username
-issuehunt: # Replace with a single IssueHunt username
-otechie: # Replace with a single Otechie username
-custom: # Replace with a single custom sponsorship URL

.gitignore

@@ -1 +1,4 @@
+.vscode/
 node_modules/
+coverage/
+lib/

.prettierignore

@@ -0,0 +1,3 @@
+node_modules/
+coverage/
+lib/

.travis.yml

@@ -1,6 +1,6 @@
 language: node_js
 arch:
-  - amd64
-  - ppc64le
+    - amd64
+    - ppc64le
 node_js:
-  - lts/*
+    - lts/*

README.md

@@ -1,6 +1,6 @@
 # nth-check [![Build Status](https://travis-ci.org/fb55/nth-check.svg)](https://travis-ci.org/fb55/nth-check)
 
-A performant nth-check parser & compiler.
+Parses and compiles CSS nth-checks to highly optimized functions.
 
 ### About
 
@@ -11,43 +11,61 @@ This module can be used to parse & compile nth-checks, as they are found in CSS
 ### API
 
 ```js
-const nthCheck = require("nth-check");
+import nthCheck, { parse, compile } from "nth-check";
 ```
 
 ##### `nthCheck(formula)`
 
-First parses, then compiles the formula.
+Parses and compiles a formula to a highly optimized function. Combination of `parse` and `compile`.
 
-##### `nthCheck.parse(formula)`
+If the formula doesn't match any elements, it returns [`boolbase`](https://github.com/fb55/boolbase)'s `falseFunc`. Otherwise, a function accepting an _index_ is returned, which returns whether or not the passed _index_ matches the formula.
 
-Parses the expression, throws a `SyntaxError` if it fails. Otherwise, returns an array containing the integer step size and the integer offset of the nth rule.
+**Note**: The nth-rule starts counting at `1`, the returned function at `0`.
 
-__Example:__
+**Example:**
 
 ```js
-nthCheck.parse("2n+3") //[2, 3]
+const check = nthCheck("2n+3");
+
+check(0); // `false`
+check(1); // `false`
+check(2); // `true`
+check(3); // `false`
+check(4); // `true`
+check(5); // `false`
+check(6); // `true`
 ```
 
-##### `nthCheck.compile([a, b])`
+##### `parse(formula)`
+
+Parses the expression, throws an `Error` if it fails. Otherwise, returns an array containing the integer step size and the integer offset of the nth rule.
+
+**Example:**
+
+```js
+parse("2n+3"); // [2, 3]
+```
+
+##### `compile([a, b])`
 
 Takes an array with two elements (as returned by `.parse`) and returns a highly optimized function.
 
-If the formula doesn't match any elements, it returns [`boolbase`](https://github.com/fb55/boolbase)'s `falseFunc`, otherwise, a function accepting an _index_ is returned, which returns whether or not a passed _index_ matches the formula. (Note: The spec starts counting at `1`, the returned function at `0`).
+**Example:**
 
-__Example:__
 ```js
-const check = nthCheck.compile([2, 3]);
-
-check(0) //false
-check(1) //false
-check(2) //true
-check(3) //false
-check(4) //true
-check(5) //false
-check(6) //true
+const check = compile([2, 3]);
+
+check(0); // `false`
+check(1); // `false`
+check(2); // `true`
+check(3); // `false`
+check(4); // `true`
+check(5); // `false`
+check(6); // `true`
 ```
 
 ---
+
 License: BSD-2-Clause
 
 ## Security contact information