JavaScript中的继承

一、原型链（默认）

function Person(){};

function Student(){};

Student.prototype = new Person();

Student.prototype.constructor = Student;

缺点：1、传参怎么搞 ？ 2、new Person的实例属性成了Student的原型属性

二、借用构造函数

function Person(name) { this.name = name;}

function Student(name, klass) { Person.call(this, name);  this.klass = klass;}

优点：传参搞定了哦  缺点：方法继承呢 继承 呢

三、组合继承（原型链+借用构造函数）

 function Person(name){
     this.name = name;
 }

 function Student(name, klass){
     Person.call(this, name);
     this.klass = klass;
 }

 Student.prototype = new Person();
 Student.prototype.constructor = Student;

还存在缺点：1、new Person的实例属性成了Student的原型属性  2 Person构造函数被调用了两次，效率低下

四、临时构造函数

 function Person(name){
     this.name = name;
 }

 function Student(name, klass){
     Person.call(this, name);
     this.klass = klass;
 }

 (function(){
     var F = function(){};
     F.prototype = Person.prototype;
     Student.prototype = new F();
     Student.prototype.constructor = Student;
 })();

看起来不错哦~~

但素，JavaScript为啥非得类式继承捏

重点来了，

原型继承

Student.prototype = Object.create(Person.prototype);

Student.prototype.constructor = Student;

原型链，链起来：new student() -----> Student.prototype----->Person.prototype-----> Object.Prototype

把你的心，我的心，串一串，串一株幸运草，串一个同心圆~~

Object.create polyfill

if(typeof Object.create !== 'function'){
    Object.create = function(o){
        var F = function(){};
        F.prototype = o;
        return new F();
    }
}

额外的，通过复制属性实现继承

 function extendDeep(parent, child){
     var i;
     child = child || {};
     for(i in parent){
         if(parent.hasOwnProperty(i)){
             if(typeof parent[i] === 'object'){
                 child[i] = (Object.prototype.toString.call(parent[i]) === '[object Array]') ? [] : {};
                 extendDeep(parent[i], child[i]);
             }else{
                 child[i] = parent[i];
             }
         }
     }
     return child;
 }