由浅入深讲解Javascript继承机制与simple-inheritance源

function SuperType(){
  this.property = true;
}
SuperType.prototype.getSuperValue = function(){
  return this.property;
}
function SubType(){
  this.subproperty = false;
}
//继承
SubType.prototype = new SuperType();
SubType.prototype.getSubValue = function(){
  return this.subproperty;
}
var instance = new SubType();

function SuperType(){
  this.colors = {"red","blue","green"}
}
function SubType(){
  SuperType.call(this);  
}
var instance = new SubType();

function SuperType(name){
  this.name = name;
  this.colors = {"red","blue","green"}
}
SuperType.prototype.sayName = function(){
  //code
}
function SubType(name,age){
  SuperType.call(this,name); 
  this.age = age;
}
SubType.prototype = new SuperType();
var instance = new SubType();

function obejct(o){
  function F(){};
  F.prototype = o;
  return new F();
}

function inheritPrototype(subType,superType){
  var prototype = object(superType.prototype);
  prototype.constructor = subType;
  subType.prototype = prototype;
}
function SuperType(name){
  this.name = name;
  this.colors = {"red","blue","green"}
}
SuperType.prototype.sayName = function(){
  //code
}
function SubType(name,age){
  SuperType.call(this,name); 
  this.age = age;
}
inheritPrototype(SubType,SuperType);
var instance = new SubTYpe();

(function(){
  //initializing用于控制类的初始化，非常巧妙，请留意下文中使用技巧
  //fnTest返回一个正则比表达式，用于检测函数中是否含有_super，这样就可以按需重写，提高效率。浏览器如果不支持的话就返回一个通用正则表达式
  var initializing = false,fnTest = /xyz/.test(function(){xyz;}) ? /\b_super\b/ : /./;
  //所有类的基类Class,这里的this一般是window对象
  this.Class = function(){};
  //对基类添加extend方法，用于从基类继承
  Class.extend = function(prop){
    //保存当前类的原型
    var _super = this.prototype;
    //创建当前类的对象，用于赋值给子类的prototype，这里非常巧妙的使用父类实例作为子类的原型，而且避免了父类的初始化(通过闭包作用域的initializing控制)
    initializing = true;
    var prototype = new this();   
    initializing = false;
    //将参数prop中赋值到prototype中，这里的prop中一般是包括init函数和其他函数的对象
    for(var name in prop){
      //对应重名函数，需要特殊处理，处理后可以在子函数中使用this._super()调用父类同名构造函数, 这里的fnTest很巧妙:只有子类中含有_super字样时才处理从写以提高效率
      prototype[name] = typeof prop[name] == "function" && typeof _super[name] == "function" && fnTest.test(prop[name])?
       (function(name,fn){
        return function(){
          //_super在这里是我们的关键字，需要暂时存储一下
          var tmp = this._super; 
          //这里就可以通过this._super调用父类的构造函数了       
          this._super = _super[name];
          //调用子类函数 
          fn.apply(this,arguments);
          //复原_super，如果tmp为空就不需要复原了
          tmp && (this._super = tmp);
        }
       })(name,prop[name]) : prop[name];
    }
    //当new一个对象时，实际上是调用该类原型上的init方法,注意通过new调用时传递的参数必须和init函数的参数一一对应
    function Class(){
      if(!initializing && this.init){
        this.init.apply(this,arguments);  
      }
    }    
    //给子类设置原型
    Class.prototype = prototype;
    //给子类设置构造函数
    Class.prototype.constructor = Class;
    //设置子类的extend方法，使得子类也可以通过extend方法被继承
    Class.extend = arguments.callee;
    return Class;
  }
})();

var Human = Class.extend({
 init: function(age,name){
  this.age = age;
  this.name = name;
 },
 say: function(){
  console.log("I am a human");
 }
});
var Man = Human.extend({
  init: function(age,name,height){
    this._super(age,name);
    this.height = height;
  }, 
  say: function(){
    this._super();
    console.log("I am a man"); 
  }
});
var man = new Man(21,'bob','191');
man.say();