Javascript継承メカニズムと構造方法チェーンの実現(元)

(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() {
		//    
		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") {
				
				//      
				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 {
				//        
				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) {
        //           
        Cat.superclass.prototype.initialize.call(this, name);  
    }  
});  
  
var BlackCat = Rs.Class(Cat, {
    initialize: function(name, type) {  
                //           
        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");

//       
cat.showName();  

// true  
alert(cat instanceof Animal);  
  
// true  
alert(cat instanceof Cat);  
  
// false  
alert(cat instanceof BlackCat);  
  
var blackCat = new BlackCat("123", "black");  
  
//       
blackCat.showName();  
  
//       
blackCat.showType();  
  
// true  
alert(blackCat instanceof Animal);  
  
// true  
alert(blackCat instanceof Cat);  
  
// true  
alert(blackCat instanceof BlackCat);