Simple JavaScript Inheritance - javascript中的简单继承

// 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;

  };

})();

 

 应用实例:

var Person = Class.extend({

  init: function(isDancing){

    this.dancing = isDancing;

  },

  dance: function(){

    return this.dancing;

  }

});

var Ninja = Person.extend({

  init: function(){

    this._super( false );

  },

  dance: function(){

    // Call the inherited version of dance()

    return this._super();

  },

  swingSword: function(){

    return true;

  }

});



var p = new Person(true);

p.dance(); // => true



var n = new Ninja();

n.dance(); // => false

n.swingSword(); // => true



// Should all be true

p instanceof Person && p instanceof Class &&
n instanceof Ninja && n instanceof Person && n instanceof Class 

原文出处：http://ejohn.org/blog/simple-javascript-inheritance/