Javascript ¼Ì³Ð»úÖƺ͹¹Ôì·½·¨Á´ÊµÏÖ

Ê×ÏÈÊÇÎÒÃÇÊìϤµÄextendº¯Êý 
/**
* À©Õ¹º¯Êý
* @param target À©Õ¹¶ÔÏó
* @param params À©Õ¹²ÎÊý
*/
function extend(target, params) {
if (!target) {
target = {};
}
for (var prop in params) {
target[prop] = params[prop];
}
return target;
}  
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/**
* ¼Ì³Ðº¯Êý
* @param SuperClass ¸¸Àà
* @param overrides ÖØд·½·¨
*/
function extendClass(SuperClass, overrides) {
var SubClass = function() {
// ×Ô¶¯µ÷Óù¹Ô캯Êý
this.initialize.apply(this, arguments);
};

SubClass.prototype = new SuperClass();

extend(SubClass.prototype, overrides);

SubClass.superclass = SuperClass;

return SubClass;
}  
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var Animal = extendClass(Object, {
initialize: function(name){
this.name = name;
},

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

var Cat = extendClass(Animal, {
initialize: function(name) {
// µ÷Óø¸À๹Ô캯Êý
Cat.superclass.prototype.initialize.call(this, name);
}
});

var BlackCat = extendClass(Cat, {
initialize: function(name, type) {
// µ÷Óø¸À๹Ô캯Êý
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");
// ¼Ì³Ð·½·¨
cat.showName();

// true
alert(cat instanceof Animal);

// true
alert(cat instanceof Cat);

// false
alert(cat instanceof BlackCat);

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

// ·½·¨ÖØд
blackCat.showName();

// ×ÔÓз½·¨
blackCat.showType();

// true
alert(blackCat i