es6-transpiler
Advanced tools
Readme
es6 -> es5
Beta
.bind using for arrow functions.concat for spread emulationStatic scope analysis and transpilation of ES6 block scoped const and let variables to ES3 based on olov/defs.
Important note: This based on the current FireFox 27 implementation. In future it has to be updated to Symbol.iterator
var obj = {a: 1, b: 2, c: 3};
obj["@@iterator"] = function() {
var iterableObject = this;
var keys = ["a", "b", "c"];
return {
next: function() {
var currentKey = keys.shift();
return {
value: currentKey ? iterableObject[currentKey] : void 0
, done: !currentKey
}
}
}
}
Install using npm
npm install es6-transpiler
Or just using Grunt 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.create
var 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:
var gulp = require('gulp');
var es6transpiler = require('gulp-es6-transpiler');
gulp.task('default', function () {
gulp.src('src/app.js')
.pipe(es6transpiler())
.pipe(gulp.dest('dist'));
});
Run it as es6toes5 <input file>. Or node --harmony es6toes5 <input file>. Also you can run a compiled es5 version node build/es5/es6toes5 <input file>.
The errors (if any) will go to stderr, the transpiled source to stdout, so redirect it like es6toes5 file.js > output.js.
require("es6-transpiler").run(<Options>)
Options is:
{
filename: string // input file
src: string // input source if not filename
outputToConsole: boolean // if true -> result would be outputted to console
outputFilename: string // if specific -> result would be written to file
}
Other options below in "Options" section.
var es6tr = require("./es6-transpiler");
var result = 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 of options object:
{
//described above:
//"filename" or "scr": "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 are
writable (true) or read-only (false), just like jshint.
environments lets you import a set of pre-defined globals, here node and
browser. These default environments are borrowed from jshint (see
jshint_globals/vars.js).
disallowVars (defaults to false) can be enabled to make
usage of var an error.
disallowDuplicated (defaults to true) errors on duplicated
var definitions in the same function scope.
disallowUnknownReferences (defaults to true) errors on references to
unknown global variables.
includePolyfills (defaults to false) 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, see LICENSE file.
See tests
es6-transpiler.js strives to transpile your program as true to the ES6 block scope semantics as
possible, while being as maximally non-intrusive as possible. The only textual
differences you'll find between your original and transpiled program is that the latter
uses var and occasional variable renames.
es6-transpiler.js detects the vast majority of cases where a variable is referenced prior to
its declaration. The one case it cannot detect is the following:
function printx() { console.log(x); }
printx(); // illegal
let x = 1;
printx(); // legal
The first call to printx is not legal because x hasn't been initialized at that point
of time, which is impossible to catch reliably with statical analysis.
v8 --harmony will detect and error on this via run-time checking. es6-transpiler.js will
happily transpile this example (let => var and that's it), and the transpiled code
will print undefined on the first call to printx. This difference should be a very
minor problem in practice.
FAQs
es6 -> es5
We found that es6-transpiler demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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