ECMAScript 6 Tools

Transpilers

Babel25k 3k - Turn ES6+ code into vanilla ES5 with no runtime
Traceur compiler8k 580 - ES6 features > ES5. Includes classes, generators, promises, destructuring patterns, default parameters & more.
es6ify476 31 - Traceur compiler wrapped as a Browserify v2 transform
babelify1k 100 - Babel transpiler wrapped as a Browserify transform
es6-transpiler171 15 - ES6 > ES5. Includes classes, destructuring, default parameters, spread
Square's es6-module-transpiler1k 107 - ES6 modules to AMD or CJS
Facebook's regenerator2k 264 - transform ES6 yield/generator functions to ES5
Facebook's jstransform - A simple utility for pluggable JS syntax transforms. Comes with a small set of ES6 -> ES5 transforms
defs132 13 - ES6 block-scoped const and let variables to ES3 vars
es6_module_transpiler-rails - ES6 Modules in the Rails Asset Pipeline
Some Sweet.js macros189 18 that compile from ES6 to ES5
Bitovi's transpile2 4 - Converts ES6 to AMD, CJS, and StealJS.
regexpu115 15 — Transform Unicode-aware ES6 regular expressions to ES5
Lebab1k 50 - Transformations for ES5 code to ES6 (approximates)

Babel: grunt-babel349 60 - Turn ES6+ code into vanilla ES5 with no runtime
Traceur: grunt-traceur247 46 ES6 > ES5 transpilation, grunt-traceur-build11 3
ES6 Module Transpiler: grunt-es6-module-transpiler80 24
Regenerator: grunt-regenerator21 2 - ES6 generator functions to ES5
grunt-microlib28 6 - tools for libs using ES6 module transpiler (sample Gruntfile3k 171 )
grunt-defs4 1 - ES6 block scoped const and let variables, to ES3
es6-transpiler: grunt-es6-transpiler12 2 - ES6 → ES5
TypeScript: grunt-ts305 122 - ES6+ > ES5/ES3 transpilation

Scratch JS300 34 - A Chrome/Opera DevTools extension to run ES6 on a page with either Babel or Traceur
generator-typescript27 5 - Yeoman generator for TypeScript apps

Mocha Traceur4 1 - A simple plugin for Mocha to pass JS files through the Traceur compiler

ES6 Module Loader polyfill2k 185 (compat with latest spec and Traceur)
js-loaders49 8 - Mozilla's spec-compliant loader prototype
JSPM - ES6, AMD, CJS module loading/package management
Babel Module Loader3k 318
beck.js6 0 - toolkit for ES6 Module Loader pipelines, shim for legacy environments

es6-boilerplate44 3 - Tooling to allow the community to use es6 now via traceur in conjunction with amd and browser global modules, with source maps, concatenation, minification, compression, and unit testing in real browsers.
es6-jspm-gulp-boilerplate164 43 - Tooling to allow the community to use es6 now via babel in conjunction jspm, with source maps, concatenation, minification, compression, and unit testing in real browsers using es6.

core-js4k 288 - Modular and compact polyfills for ES6 including Symbols, Map, Set, Iterators, Promises, setImmediate, Array generics, etc. The standard library used by Babel25k 3k .
es6-shim2k 258 - almost all new ES6 methods — from Map, Set, String, Array, Object, Object.is and more.
WeakMap, Map, Set, HashMap - ES6 Collections123 15
Polymer's WeakMap shim30 12
String.prototype.startsWith
String.prototype.endsWith
String.prototype.at
String.prototype.repeat
String.prototype.includes
String.prototype.codePointAt
String.fromCodePoint
Array.prototype.find
Array.prototype.findIndex
Array.from
Array.of
Object.assign
Number.isFinite
Math.sign
RegExp.prototype.match
RegExp.prototype.search
es6-promise3k 171 - polyfill for Promises matching the ES6 API
ES6 Map Shim10 0 - destructive shim that follows the latest specification as closely as possible.
Function.create
ES6 shim929 234
ES6 Symbol polyfill79 16
ES6 Map, Set, WeakMap5 0
harmony-reflect381 54 - ES6 reflection module (contains the Proxy API)
ES5 based shims in pure CJS style - Array, Object, Number, Math and String functions/methods, plus Map, Set, Symbol and WeakMap objects

ES6 syntax highlighting for Sublime Text and TextMate214 18
ES6 syntax support in WebStorm and PhpStorm, compilation to ES5 with file watchers or task runners
DocPad plugin2 0 for Traceur
Grammar and transpilation package486 101 for Atom
Learn ES6 transpilation options in Webstorm Read Blog Post

Esprima - JavaScript parser supporting ES6, parses to ESTree AST format1k 141
Acorn2k 202 - A small, fast, JavaScript-based JavaScript parser with ES6 support, parses to SpiderMonkey AST format.
esparse106 11 - ES6 parser written in ES6.
Traceur compiler8k 580 also has built-in parser available under traceur.syntax.Parser.

ES.next showcase182 7 - real-world usage examples of ES6 features
looper9 0 - static analysis tools for ES6
es6-module-packager
es-dependency-graph6 4 and grunt-es-dependency-graph2 2 - Generate a list of imports and exports from ES6 module files, useful for preloading, bundling, etc.
es6-import-validate4 1 and grunt-es6-import-validate3 1 - validate matching named/default import statements in ES6 modules.
let-er29 2 - transpiles let-block block-scoping (not accepted into ES6) into either ES3 or ES6
Recast2k 171 - Esprima-based JavaScript syntax tree transformer, conservative pretty-printer, and automatic source map generator. Used by several of the transpilers listed above, including regenerator2k 264 and es6-arrow-function31 8 .
Paws on ES636 4 - Minimalist examples of ES6 functionalities.
ES6 on node - How to use ES6 features in node.js.
es6-translate4 0 - Uses the ES6 loader hooks to load (node flavored) commonjs packages in ES6.
Isparta693 78
babel-node - Run node cli with ES6 transpiling using Babel.
ES6 Lab setup49 8 - A simple setup for transpiling ES6 to ES5 using Babel or traceur with gulp and jasmine support.
TypeScript - A superset of ECMAScript with strict typing that aims to align with ES6
Rollup - Rollup is a next-generation JavaScript module bundler. Author your app or library using ES2015 modules, then efficiently bundle them up into a single file for use in browsers and Node.js