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js面向对象(2)

js面向对象(2)

作者: 悟空你又瘦了 | 来源:发表于2018-01-31 10:11 被阅读0次

    4.js里面的继承

    1.混入式继承(mix-in)
    //继承1个对象
    var o = {
               extend: function(obj){
                for(var k in obj){
                   this[k] = obj[k];
                 }
              }
           };
      o.extend(o1);
    //继承多个对象
       var o = {
               extend: function(){
                   for (var i = 0; i < arguments.length; i++) {
                       var obj = arguments[i];
    
                       for(var k in obj){
                           this[k] = obj[k];
                       }
                   }
               }
           }
    
       o.extend(o1, o2, o3, o4);
    
    2.经典继承(Object.create)
    语法:var obj = Object.create(obj1);
    含义:创建一个对象obj,并且继承了obj1
    不兼容ie8以下
     function myCreate (obj){
            if (Object.creat) {
                return Object.creat(obj)
            } else{
                function F(){};
                F.prototype = obj;
                return new F ();
            }
            
        }
    3.继承的方式也有很多种:原型链继承、借用构造函数继承、组合继承、原型式继承、寄生式继承、寄生组合式继承……
    
    WTF ! 简直要吐血有木有
    
    那就用一种自己最熟练的就好了,形成自己的风格吧!
    
    
    //组合使用构造函数模式和原型模式  创建对象
    //父类
    function Person(name){
        this.name = name || "Tom";
        this.age = "12";
        //实例方法 (不会被覆盖)
        this.say = function(){
            console.log("Hello " + this.name + "!");
        }
    }
    //原型方法
    Person.prototype.run = function(){
        console.log(this.name + " is running");
    }
    Person.prototype.eat = function(food){
        console.log(this.name + " is eating " + food);
    }
    
    /*更方便的写法:
     * Person.prototype = {   //这里相当于完全重写了默认的prototype对象,constructor属性也变成了新的对象的constructor属性(指向Object)
        constructor: Person,  //将构造器重新指向Person
        run: funtion(){
            console.log(this.name + " is running");
        },
        eat: function(){
            console.log(this.name + " is eating " + food);
        }
    }*/
    
    //组合继承:通过调用父类构造函数,继承父类的属性并保留传参的优点,然后通过将父类实例作为子类原型,实现函数复用
    //子类
    function People(name){
        Person.call(this);  //构造函数继承 (调用父类构造函数)
        this.name = name || "Rose"; //修改继承的属性
        this.sport = "football";  //自定义新的属性
    }
    
    People.prototype = new Person(); //原型继承 (将父类实例作为子类原型)
    
    People.prototype.say = function(){  //修改继承的方法
        console.log("Hello " + this.name + " you are welcome");
    }
    
    People.prototype.run = function(){  //修改继承的方法
        console.log(this.name + " is go go go");
    }
    
    People.prototype.play = function(){  //自定义新的方法
        console.log(this.name + " is playing " + this.sport);
    }
    
    //test
    var person1 = new People("Jack");
    console.log(person1.name);      //Jack
    console.log(person1.age);       //12                  //继承原型的属性
    person1.say();                  //Hello Jack!   //实例方法无法在其原型上修改。  如此修改:person1.say(){ balabala }
    person1.run();                  //Jack is go go go    //覆盖了原型方法
    person1.eat("apple");           //Jack is eating apple
    
    var person2 = new People("Lucy");
    console.log(person2.name);      //Lucy
    console.log(person2.age);       //12                  //继承原型的属性
    person2.say();                  //Hello Lucy!   //实例方法无法在其原型上修改 
    person2.run();                  //Lucy is go go go    //覆盖了原型方法
    person2.eat("apple");           //Lucy is eating apple
    person2.play();                 //Lucy is playing football
    

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