Class属性Extends和Implements的区别

var Animal = new Class({
    initialize: function(age){
        this.age = age;
    }
});
var Cat = new Class({
    Extends: Animal,
    initialize: function(name, age){
        this.parent(age); // calls initalize method of Animal class
        this.name = name;
    }
});
var myCat = new Cat('Micia', 20);
console.log(myCat.name); //'Micia'.
console.log(myCat.age); // 20.

var Dog = new Class({    Implements: Animal,    setName: function(name){        this.name = name    }});var myAnimal = new Dog(20);console.log(myAnimal.age);myAnimal.setName('Micia');console.log(myAnimal.name); //  'Micia'.

通过Extends实现继承时，需要通过调用parent方法来调用父元素的initialize方法从而继承父元素的属性

而通过Implements实现继承时，直接就可以继承父元素的属性，这种方式很适合父类不止一个的情况下

另外额外补充类方法Implement和extend，这两个方法用于扩展已经定义了的类

var Animal = new Class({
    initialize: function(age){
        this.age = age;
    }
});
Animal.implement({
    setName: function(name){
        this.name = name;
    }
});
var myAnimal = new Animal(20);
myAnimal.setName('Micia');
console.log(myAnimal.name); //'Micia'

“The main difference between extend and implement is that Implement changes the class's prototype, while Extend creates a copy. This means that if you implement a change into a class all instances of that class will inherit that change instantly, while if you useExtend then all existing instances will remain the same。”

简单翻译下:extend和implement的主要区别是，implement改变了类的prototype属性，而extend只是新建了一个副本。这意味着如果你通过implement对类做了改变，那将改变他的所有实例，而通过extend改变类的话，不会改变在此之前存在的实例。

var Thingy = new Class({
go: function(){
alert('hi');
}
});

var myClass = new Thingy();
myClass.go(); /* alerts 'hi' */

Thingy.implement({
go: function(){
alert('implemented');
}
});
myClass.go(); /* alerts 'implemented' */
Thingy = Thingy.extend({
go: function(){
alert('extended');
}
});
myClass.go(); /* alerts 'implemented'
                 because extend only affects
                 new instances. */