Javascript 繼承機制和構造方法鏈實現(原)

(function(){
	Rs = {version: 1.0};

	Rs.extend = function(target, params) {

		target = target || {};

		for (var prop in params) {
			target[prop] = params[prop];
		}	
		return target;
	};

	Rs.Class = function() {
		// 構造體
		var Class = function() {
			this.initialize.apply(this, arguments);
		};

		var extended = {};

		var parent, superclass;

		for (var index = 0, len = arguments.length; index < len; index++) {

			if (typeof arguments[index] == "function") {

				// 如果有父類
				if (index == 0 && len > 1) {

					var initialize = arguments[index].prototype.initialize;

					arguments[index].prototype.initialize = function() {};

					extended = new arguments[index]();

					if (initialize === undefined) {
						delete arguments[index].prototype.initialize;
					} else {
						arguments[index].prototype.initialize = initialize;
					}

					superclass = arguments[index];
					continue;
				}

				parent = arguments[index].prototype;
			} else {
				// 如果爲頂層基類
				parent = arguments[index];
			}

			Rs.extend(extended, parent);
		}
		Class.prototype = extended;
		Class.superclass = superclass;
		return Class;
	};
})();

var Animal = Rs.Class({
    initialize: function(name){

        this.name = name;  
    },

    showName: function(){    
        alert(this.name);    
    }  
});

var Cat = Rs.Class(Animal, {
    initialize: function(name) {
        // 調用父類構造函數  
        Cat.superclass.prototype.initialize.call(this, name);  
    }  
});  

var BlackCat = Rs.Class(Cat, {
    initialize: function(name, type) {  
                // 調用父類構造函數  
        BlackCat.superclass.prototype.initialize.call(this, name);  
        this.type = type;  
    },  
    showType: function() {  
        alert(this.type);  
    },  
    showName: function() {  
        alert(this.name + ":" + this.type);  
    }  
});  


var cat = new Cat("cat name");

// 繼承方法  
cat.showName();  

// true  
alert(cat instanceof Animal);  

// true  
alert(cat instanceof Cat);  

// false  
alert(cat instanceof BlackCat);  

var blackCat = new BlackCat("123", "black");  

// 方法重寫  
blackCat.showName();  

// 自有方法  
blackCat.showType();  

// true  
alert(blackCat instanceof Animal);  

// true  
alert(blackCat instanceof Cat);  

// true  
alert(blackCat instanceof BlackCat);

大家可能會問，Rs是什麼，Rs就是Rainsilence的簡稱。^-^

以上實現了繼承，多態，重載，和完整的構造體方法鏈。