sweet.js

Hygienic Macros for JavaScript!

• Documentation at sweetjs.org.
• Overview and motivation in this talk.
• Example macros on the wiki.
• Mailing list for discussion
• IRC channel #sweet.js on irc.mozilla.org

Use

Using Node

Install with npm:

$ npm install -g sweet.js

To try it out make a file test_macros.sjs:

// functions can now be spelled def!
macro def {
  case $name:ident $params $body => {
    function $name $params $body
  }
}
def add (a, b) {
  return a + b;
}

console.log( add(3, 7) );

And compile it with sjs:

$ sjs -o output.js test_macros.sjs
$ node output.js
10

Alternately you can require an sjs file from node. For example, in main.js add:

var sjs = require('sweet.js'),
    example = require('./example');

example.one;

Where ./example.sjs contains:

macro A {
    case ($a + $b) => {
        $a
    }
}

exports.one = A(1 + 2);

And just run main.js in node.

Using AMD in the browser

An AMD loader is provided at require-sweet.

define(['sweeten!a/javascript/dep-with-macros'], function(dep) {
  // dep is compiled to JS at this point.
});

Hacking

Install the dev dependencies:

$ npm install

Build and run the tests:

$ node build

Sweet.js is self hosted so the files in src/ are compiled with the files in lib/ and then copied into build/lib/. Then the tests in test/ are compiled with build/lib/. Once you are happy with your changes run node build build_sweetjs to compile sweet.js into lib/ which can then be checked into git.

Slightly confusing but the process goes like this:

<hack hack hack>
$ node build
<tests fail!>
<hack hack hack>
$ node build
<tests pass!>
$ node build build_sweetjs
$ git add lib/
$ git commit -m "sweet!"