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Source transformer enabling ECMAScript 6 generator functions (yield) in JavaScript-of-today (ES5)

regenerator Build Status

This package implements a fully-functional source transformation that takes the syntax for generators/yield from ECMAScript 2015 or ES2015 and Asynchronous Iteration proposal and spits out efficient JS-of-today (ES5) that behaves the same way.

A small runtime library (less than 1KB compressed) is required to provide the wrapGenerator function. You can install it either as a CommonJS module or as a standalone .js file, whichever you prefer.


From NPM:

npm install -g regenerator

From GitHub:

cd path/to/node_modules
git clone git://github.com/facebook/regenerator.git
cd regenerator
npm install .
npm test


You have several options for using this module.

Simplest usage:

regenerator es6.js > es5.js # Just the transform.
regenerator --include-runtime es6.js > es5.js # Add the runtime too.
regenerator src lib # Transform every .js file in src and output to lib.

Programmatic usage:

var es5Source = require("regenerator").compile(es6Source).code;
var es5SourceWithRuntime = require("regenerator").compile(es6Source, {
  includeRuntime: true

AST transformation:

var recast = require("recast");
var ast = recast.parse(es6Source);
ast = require("regenerator").transform(ast);
var es5Source = recast.print(ast);

How can you get involved?

The easiest way to get involved is to look for buggy examples using the sandbox, and when you find something strange just click the "report a bug" link (the new issue form will be populated automatically with the problematic code).

Alternatively, you can fork the repository, create some failing tests cases in test/tests.es6.js, and send pull requests for me to fix.

If you're feeling especially brave, you are more than welcome to dive into the transformer code and fix the bug(s) yourself, but I must warn you that the code could really benefit from better implementation comments.

Pincer is a project which aims to provide best library discovery tools for developers. We're growing day by day. We have only npm platform for now but we will add the others as much as we can.