浅谈JavaScript 继承机制的实现(3)

来源：未知责任编辑：责任编辑发表时间:2014-01-25 11:36　点击:次

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Sex.apply(this,[sex]); //apply()方法
}
var chin1 = new Chinese("小明","Male");
这里是call()和apply()方法的介绍:http://www.w3school.com.cn/js/pro_js_inheritance_implementing.asp

其实对象冒充最大的问题就是,无法通过子类找到继承的父类.

所以这并非真正意义的继承.

[javascript]
chin1 instanceof Chinese; //true
chin1 instanceof Human; //false
chin1 instanceof Sex; //false
chin1 instanceof Chinese; //true
chin1 instanceof Human; //false
chin1 instanceof Sex; //false

当继承的父类中有定义对应的方法时,每次定义的对象都会重新生成一个对应的方法,这样十分浪费内存,而且不便于管理.

[javascript]
function Human(){       //定义Human类
    this.species = "Human";
    this.fun = function() {};
}
function Sex(sex) {     //定义Sex类
    this.sex = sex;
}
function Chinese(name,sex){
    this.name = name;
    Human.call(this);   //call()方法
    Sex.apply(this,[sex]); //apply()方法
}
var chin1 = new Chinese("小明","Male");
var chin2 = new Chinese("小红","Female");
chin1.fun === chin2.fun; //false
function Human(){   //定义Human类
this.species = "Human";
this.fun = function() {};
}
function Sex(sex) { //定义Sex类
this.sex = sex;
}
function Chinese(name,sex){
this.name = name;
Human.call(this); //call()方法
Sex.apply(this,[sex]); //apply()方法
}
var chin1 = new Chinese("小明","Male");
var chin2 = new Chinese("小红","Female");
chin1.fun === chin2.fun; //false

因此,下面要讨论的是原型继承(prototype).
[javascript]
function Human(){       //定义Human类
    this.species = "Human";
}
function Chinese(name){
    this.name = name;
}
Chinese.prototype = new Human(); //原型对象指向Human类