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es6 -> es5

Beta

• different output thantraceur-compiler:
  1. no runtime library (only polyfills if needed)
  2. no try/catch for block binding
  3. spread:* via.concat* should respect Iterator protocol* spread is operator, not a function
  4. minimal count of temporary variables
  5. termination stage for temporary variables
  6. es6 RegExp support
  7. and others
• output should supportClosure Compiler
• line-to-line input/output mapping

• classes
• generator comprehensions
• destructuring (with default values)
• block binding (let / const)
  • loops: fresh lexical environment per iteration
• function default parameters and rest
• arrow functions
• spread (with iterator protocol)
• for-of (with iterator protocol)
• array comprehensions (with iterator protocol)
• string templates (with tags support)
• object literals:
  • methods
  • shorthands
  • computed properties
• binary/octal numericLiteral
• unicode code point escapes
• RegExp:
  • 'y' flag support (in runtime via polyfill)
  • 'u' flag support:
    • full transpiler-time support: [negative] astral symbols (surrogate pairs) ranges, \D, \W, '.' etc captures astral symbols
    • partial runtime support see:Not supported

Static scope analysis and transpilation of ES6 block scopedconst andlet variables to ES3 based onolov/defs.

• modules
• generators
• symbols
• RegExp:
  • 'u' flag in runtime (via polyfill) for the newly generated patterns:
    1. \D, \W, '.' etc not supported
    2. negative astral symbols (surrogate pairs) ranges

varobj={a:1,b:2,c:3};varSymbol_iterator=typeofSymbol!=='undefined'&&Symbol.iterator||"@@iterator";obj[Symbol_iterator]=function(){variterableObject=this;varkeys=["a","b","c"];return{next:function(){varcurrentKey=keys.shift();return{value:currentKey ?iterableObject[currentKey] :void0,done:!currentKey}}}}

Install using npm

npm install es6-transpiler

Or just usingGrunt task (see below).

For the output code works you need an implementation of Object.create in the target browser.You can get it here:es5-shim or copy and past this code:

if(!Object.create)Object.create = function(_prototype) {//[Warning!!!]This is PURE and UNSAFE implementation of Object.createvar Type = function () {};Type.prototype = _prototype;var _object = new Type();_object.__proto__ = _prototype;return _object;};

Grunt task can be fount here:https://github.com/termi/grunt-es6-transpiler

Install:npm install grunt-es6-transpiler

Usage:

grunt.loadNpmTasks('grunt-es6-transpiler');grunt.initConfig({"es6-transpiler":{test:{src:'test.js',dest:'test.es5.js'}},})

Gulp task can be fount here:https://github.com/sindresorhus/gulp-es6-transpiler

Install:npm install --save-dev gulp-es6-transpiler

Usage:

vargulp=require('gulp');vares6transpiler=require('gulp-es6-transpiler');gulp.task('default',function(){gulp.src('src/app.js').pipe(es6transpiler()).pipe(gulp.dest('dist'));});

Run it ases6toes5 <input file>. Ornode --harmony es6toes5 <input file>. Also you can run a compiled es5 versionnode build/es5/es6toes5 <input file>.The errors (if any) will go to stderr, the transpiled source tostdout, so redirect it likees6toes5 file.js > output.js.

require("es6-transpiler").run(<Options>)

Options is:

{filename: string // input filesrc: string // input source if not filenameoutputToConsole: boolean // if true -> result would be outputted to consoleoutputFilename: string // if specific -> result would be written to file}

Other options below in "Options" section.

vares6tr=require("./es6-transpiler");varresult=es6tr.run({filename:"test.js"});console.log(result.src);//result

result object is:

{    src: string or "" // on success    errors: array of error messages or [] // on errors    stats: statistics object    ast: transformed ast // ast tree from esprima    getNeedfulList: <function: Array.<string>> // list of necessary polyfills    getNeedfulLib: <function: string> // text of necessary polyfills    getFullLib: <function: string> // text of all available polyfills}

Example ofoptions object:

{//described above://"filename" or "src": "string"//outputToConsole: false//outputFilename: true    "environments": ["node", "browser"],    "globals": {        "my": false,        "hat": true    },    "disallowVars": false,    "disallowDuplicated": true,    "disallowUnknownReferences": true,    "includePolyfills": <boolean> | <"full">,    "polyfillsSeparator": <string>}

globals lets you list your program's globals, and indicate whether they arewritable (true) or read-only (false), just likejshint.

environments lets you import a set of pre-defined globals, herenode andbrowser. These default environments are borrowed fromjshint (seejshint_globals/vars.js).

disallowVars (defaults tofalse) can be enabled to makeusage ofvar an error.

disallowDuplicated (defaults totrue) errors on duplicatedvar definitions in the same function scope.

disallowUnknownReferences (defaults totrue) errors on references tounknown global variables.

includePolyfills (defaults tofalse) insert polyfills in the output file.true - insert only the necessary polyfills."full" - insert all available polyfills.

polyfillsSeparator (default - empty string) any string that should be inserted before polyfills library.

MIT, seeLICENSE file.

See tests

es6-transpiler.js strives to transpile your program as true to the ES6 semantics aspossible, while being as maximally non-intrusive as possible.

es6-transpiler.js detects the vast majority of cases where a variable is referenced prior toits declaration. The one case it cannot detect is the following:

functionprintx(){console.log(x);}printx();// illegalletx=1;printx();// legal

The first call toprintx is not legal becausex hasn't been initialized at that pointoftime, which is impossible to catch reliably with statical analysis.v8 --harmony will detect and error on this via run-time checking.es6-transpiler.js willhappily transpile this example (let =>var and that's it), and the transpiled codewill printundefined on the first call toprintx. This difference should be a veryminor problem in practice.

1. Generators support
2. Modules support
3. 'pre-es6-node10', 'pre-es6-chrome20' and 'pre-es6-ff24' output modes