Aspect Oriented Programming for Javascript. It allows you to change the behavior of, or add behavior to methods and functions (including constructors) non-invasively.

As a simple example, instead of changing code, you can use meld to log the result of myObject.doSomething:

var myObject = {
    doSomething: function(a, b) {
        return a + b;
    }
};

// Call a function after myObject.doSomething returns
var remover = meld.after(myObject, 'doSomething', function(result) {
    console.log('myObject.doSomething returned: ' + result);
});

myObject.doSomething(1, 2); // Logs: "myObject.doSomething returned: 3"

remover.remove();

myObject.doSomething(1, 2); // Nothing logged

Docs

• API
• Reference
• Aspects

Quick Start

AMD

1. Get it using one of the following

   1. yeoman install meld, or
   2. bower install meld, or
   3. git clone https://github.com/cujojs/meld, or
   4. git submodule add https://github.com/cujojs/meld

2. Configure your loader with a package:

   packages: [
       { name: 'meld', location: 'path/to/meld', main: 'meld' },
       // ... other packages ...
   ]

3. define(['meld', ...], function(meld, ...) { ... }); or require(['meld', ...], function(meld, ...) { ... });

Node

1. npm install meld
2. var meld = require('meld');

RingoJS

1. ringo-admin install cujojs/meld
2. var meld = require('meld');

Running the Unit Tests

Install buster.js

npm install -g buster

Run unit tests in Node:

buster test

What's New

1.3.0

• meld() is now a function that adds aspects.
  • DEPRECATED: meld.add(). Use meld() instead.

1.2.2

• Remove stray console.log.

1.2.1

• Fix for IE8-specific issue with meld's internal use of Object.defineProperty.
• Internally shim Object.create if not available to so that meld no longer requires an Object.create shim to advise constructors in pre-ES5 environments.

1.2.0

• meld.joinpoint() - Access the current joinpoint from any advice type.
• Bundled aspects:
  • trace: trace method call entry/return/throw
  • memoize: simple memoization for methods and functions
  • cache: configurable caching aspect to do more than simple memoization

1.1.0

• Advice can be applied directly to methods on a function.
• Removed undocumented behavior that implicitly adds constructor prototype advice: to advise a prototype, pass the prototype as the advice target.

1.0.0

• Removed browser global - window.meld is no longer supported. See this post on the cujo.js Google Group for an explanation.
• No functional change beyond browser global removal.

See the full Changelog here

References

• AspectJ and Spring Framework AOP for inspiration and great docs
• Implementation ideas from @phiggins42's uber.js AOP
• API ideas from jquery-aop