/* 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; 
 }; 
})();

var Person = Class.extend({ ① 
 init: function (isDancing) { ② 
 this.dancing = isDancing; 
 }, 
 dance: function () { ③ 
 return this.dancing; 
 } 
}); 
 
 
var Ninja = Person.extend({ ④ 
 init: function () { ⑤ 
 this._super(false); ⑥ 
 }, 
 dance: function () { ⑦ 
 // Call the inherited version of dance() 
 return this._super(); ⑧ 
 }, 
 swingSword: function () { ⑨ 
 return true; 
 } 
}); 
 
 
var p = new Person(true); ⑩ 
console.log(p.dance());// true 
 
 
var n = new Ninja(); 
console.log(n.dance()); // false 
console.log(n.swingSword()); // true