gistfile1.js

/*
 *    def.js: Simple Ruby-style inheritance for JavaScript
 *
 *    Copyright (c) 2010 Tobias Schneider
 *    This script is freely distributable under the terms of the MIT license.
 *
 *
 *    Example:
 *    
 *      def ("Person") ({
 *          init: function(){ ... }
 *      });
 *
 *      def ("Ninja") << Person ({
 *          init: function(){ ... }
 *      });
 */
(function(global) {

  // dummy subclass
  function Subclass() { }

  function augment(destination, source) {
    // TODO: Ensure we fix IE to iterate over shadowed properties
    // of those further down the prototype chain. There is also a
    // bug in Safari 2 that will match the shadowed property and
    // the one further down the prototype chain.
    for (var key in source)
      destination[key] = source[key];
  }

  function def(klassName, context) {

    // create the `Class` on the given context (defaults to the global object)
    var Klass =
    (context || global)[klassName] = function Klass() {
      // called with the `new` operator
      if (this != global) {
        // allow the init method to return a different class/object
        return this.init && this.init.apply(this, arguments);
      }

      // called as a method
      // defer setting up a superclass and adding plugins
      def._super = Klass;
      def._plugins = arguments[0] || { };
    },

    // static helper method
    addPlugins =
    Klass.addPlugins = function addPlugins(plugins) {
      augment(Klass.prototype, plugins);
    };

    // we use valueOf to finish the setup of the
    // deferred superclass and added plugins
    addPlugins.valueOf = function() {
      var Superclass = def._super;
      if (Superclass) {
        Subclass.prototype = Superclass.prototype;
        Klass.prototype = new Subclass;
      }
      addPlugins(def._plugins);
      def._super = def._plugins = null;
    };

    return addPlugins;
  }

  // expose
  global.def = def;
})(this);


// Usage

def ('Person') ({
  'init': function(name) {
    this.name = name;
  },
  'speak': function(text) {
    alert(text || 'Hi, my name is ' + this.name);
  }
});

def ('Ninja') << Person ({
  'kick': function() {
    this.speak('I kick u!');
  }
});

var ninjy = new Ninja('JDD');
ninjy.speak();
ninjy.kick();