mutoo
2/14/2014 - 2:32 AM

simple_javascript_inheritance.js

/* Simple JavaScript Inheritance
 * By John Resig http://ejohn.org/
 * MIT Licensed.
 */
// Inspired by base2 and Prototype
(function() {
  var initializing = false,
    fnTest = /xyz/.test(function() {
      xyz;
    }) ? /\b_super\b/ : /.*/;

  // The base Class implementation (does nothing)
  this.Class = function() {};

  // Create a new Class that inherits from this class
  Class.extend = function(prop) {
    var _super = this.prototype;

    // Instantiate a base class (but only create the instance,
    // don't run the init constructor)
    initializing = true;
    var prototype = new this();
    initializing = false;

    // Copy the properties over onto the new prototype
    for (var name in prop) {
      // Check if we're overwriting an existing function
      prototype[name] = typeof prop[name] == "function" &&
        typeof _super[name] == "function" && fnTest.test(prop[name]) ?
        (function(name, fn) {
        return function() {
          var tmp = this._super;

          // Add a new ._super() method that is the same method
          // but on the super-class
          this._super = _super[name];

          // The method only need to be bound temporarily, so we
          // remove it when we're done executing
          var ret = fn.apply(this, arguments);
          this._super = tmp;

          return ret;
        };
      })(name, prop[name]) :
        prop[name];
    }

    // The dummy class constructor
    function Class() {
      // All construction is actually done in the init method
      if (!initializing && this.init)
        this.init.apply(this, arguments);
    }

    // Populate our constructed prototype object
    Class.prototype = prototype;

    // Enforce the constructor to be what we expect
    Class.prototype.constructor = Class;

    // And make this class extendable
    Class.extend = arguments.callee;

    return Class;
  };
})();