bring tomorrow's Harmony to today's JavaScript
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A "transpiler" that brings tomorrow's Harmony to today's JavaScript.

Note: I don't plan on working on this code any more. See Traceur for a more active project. Thanks.


  • Harmony modules to AMD, Node.js, or Revealing Module Pattern
  • Shorthand properties
  • Method definitions
  • Arrow functions (requires Function.prototype.bind)
  • Class declarations
  • Maintains line numbers


Look in the demo directory or try it here.


$ npm install harmonizr


$ ./node_modules/.bin/harmonizr [options] path/to/input

If you install Harmonizr globally or have ./node_modules/.bin in your PATH, you can omit the path to the harmonizr script.

Specify --amd, --node, or --revealing to transform Harmony-style modules into AMD, Node.js, or JavaScript Revealing Module Pattern- style modules.

This transpiles src/foo.js into a Node.js-compatible version at lib/foo.js:

$ harmonizr --node --output lib/foo.js src/foo.js

Use --module to implicitly wrap the entire file in a module declaration. The name of the module is required, but only appears in the output when using --revealing.

Use --relatives with --node to indicate what modules should be loaded from the local directory and not the node_modules directory.

For example, if a foo module needs to load bar and baz modules from the same directory as it (not from node_modules), you could do this:

$ harmonizr --node --relatives bar,baz --output lib/foo.js src/foo.js


  • No nested modules.
  • No import * from module;.
  • export is only allowed when in front of a simple function or variable declaration.
  • Probably bugged.


Harmonizr uses the excellent Esprima parser. A copy of Esprima from its "harmony" branch is embedded into Harmonizr in the lib directory.

The actual source code for Harmonizr is in the src directory. The Makefile transpiles that into a Node.js-style module in lib, AMD-style in demo, and Revealing Module Pattern-style in test.

Harmonizr transpiles itself. Since Node.js doesn't support the newer syntax harmonizr.js uses in the src directory, it loads the harmonizr module out of the lib directory. Be careful when building.

Tests are in the test directory. Run them with npm test or by opening test.html.

If you'd like to contribute, please try to include tests, ensure the code coverage stays at 100%, and that JSHint doesn't complain.

Execute make to build, run JSHint, and run the tests (with code coverage).