ECMAScript 6 to 5 Compiler and Runtime Environment
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This repository is no longer actively maintained. Current work on this technology has moved to esdown.


es6now is an ES6 to ES5 compiler, written in ES6. It will allow you to write programs using next-generation Javascript features without having to wait for Node or browsers to fully implement ES6.

es6now can also be used as a runtime environment for executing ES6 programs on top of Node.

Source maps are not required when debugging code translated with es6now. One of the fundamental design goals is that the output should look like the input. Line numbers, whitespace and comments are all maintained.

For more information:

  • The Feature Guide describes the ES6 features that you can use with es6now.
  • The Module Guide describes the ES6 module system implemented in es6now.


Install globally with NPM (you may need to sudo this):

npm install -g es6now

Start a REPL by running it without any arguments:


Execute a module by adding a path:

es6now main.js

Translate a module by using a hyphen:

es6now - src/main.js build/es6now.js -b -r

--input, -i  (1)    The file to translate.
--output, -o (2)    The file to write to. If not set, then the output
                    will be written to the console.
--bundle, -b        If present, module dependencies will be bundled
                    together in the output.
--runtime, -r       If present, the es6now runtime code will be bundled
                    with the output.
--global, -g        If specified, the name of the global variable to
                    dump this module's exports into, if the resulting
                    script is not executed within any module system.


es6now can also be used as a library. First, install locally with NPM:

npm install es6now

translate(input, options = {})

Translates ES6 code to ES5. The following options are defined:

  • module: (Boolean) If true, parse the input as a module. Otherwise, parse the input as a script. The default is false.
  • runtime: (Boolean) If true, include the es6now runtime library in the output. The default is false.
  • wrap: (Boolean) If true, wrap the output in boilerplate which will ensure compatibility with Node and AMD modules. The default is false.
  • global: (String) If specified, the name of the global variable which will be used to expose the module if it is loaded as a plain script in the browser.


var es6now = require("es6now");

var output = es6now.translate("class C { foo() {} }", {
    module: true,
    wrap: true