sweet.js

Hygienic Macros for JavaScript!

• Documentation at sweetjs.org.
• Online editor
• 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.js:

// functions can now be spelled def!
macro def {
  rule { $name $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.js
$ node output.js
10

If you want to collect your macro definitions into a separate file you can use the -m flag:

$ sjs -m macros.js -o output.js main.js 

Where the macros defined in macros.js that you want to be available in main.js are exported with the keyword export:

// macros.js

macro m { /* ... */ }
export m;

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:

$ grunt

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 grunt dist to compile sweet.js into lib/ which can then be checked into git.

Slightly confusing but the process goes like this:

<hack hack hack>
$ grunt
<tests fail!>
<hack hack hack>
$ grunt
<tests pass!>
$ grunt dist
$ git add lib/
$ git commit -m "sweet!"