Shepherd.js - Implementing Harmony modules for today's browsers

Xavier CAMBAR xcambar at
Wed Apr 18 05:20:11 PDT 2012

I wanted to announce that I've been working on a project called Shepherd (, a pure Javascript implementation of
Harmony modules.

Why such a project ? Fun first. Second, I was really looking forward to use
harmony modules. Third, I wanted an efficient way to use my modules on the
server and the client. And it seems to me that current module loaders and
APIs available will be, at the end, superseded by the module syntax being
defined at ECMA for the future versions of ECMAScript.

The syntax used is as of 2012-02-27 (, I
couldn't find the time to implement the latest proposal (besides I would
have had to choose one of the two variants), but apart from the syntax, it
is usable both on the client and the server, and tested.

The parser/lexer has been developped using JISON ( and is available as a separate project (

For backward-compatibility, the module declarations have to be put into
comments (which you will discover in the examples provided on the site), it
is compatible with CommonJS modules (user-defined as well as native modules
in Node.js), and, although not critical to the project, a compatibility
wrapper for the AMD API is on its way.
Regarding production-level requirements, an optimizer has been implemented,
but it still requires testing before being released.

I've had and I'm still having a really good time working on this project
and I would really appreciate if I could have some feedback from the
readers and contributors of the mailing-list.
A mailing list has been created for the project, still empty of messages
simply because it has been created yesterday ;)


@xcambar <!/xcambar>
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