js继承的方式

原型链继承

 function Parent(){
            this.name='mike';
            this.age=12;
          }
          function Child(){
            
          }
          //儿子继承父亲（原型链）
          Child.prototype=new Parent();//Child继承Parent，通过原型形成链条
          var test=new Child();
          console.log(test.age);
          console.log(test.name);//得到被继承的属性
          //孙子继续原型链继承儿子
          function Brother(){
            this.weight=60;
          }
          Brother.prototype=new Child();//继承原型链继承
          var brother=new Brother();
          console.log(brother.name);//继承了Parent和Child，弹出mike
          console.log(brother.age);//12
           console.log(brother.weight);
           //instanceof 就是判断一个实例是否属于某种类型
          console.log(brother instanceof Child);//ture
          console.log(brother instanceof Parent);//ture
          console.log(brother instanceof Object);//ture

call和apply函数的继承

call和apply都可以实现函数的继承

function Parent(age){
            this.name=['mike','jack','smith'];
            this.age=age;
          }
          function Child(age){
           Parent.call(this,age);//让Child拥有Parent的属性
           Parent.apply(this,[age]);
          }
          var test=new Child(21);
          console.log(test.age);//21
          console.log(test.name);
          test.name.push('bill');
          console.log(test.name);//mike,jack,smith,bill

call和apply的区别是穿的参数不同

call和apply都接收两个参数，第一个参数都是thisobj

apply的第二个参数必须是有效数组或arguments对象

call的第二个参数必须列举出来

var myObject = {firstName:'my', lastName:'Object'};

        function getMessage(sex,age){
            console.log(this.firstName + this.lastName + " 性别: " + sex + " age: " + age );
        }
         getMessage.apply(myObject,["未知",22]);//myObject 性别: 未知 age: 22
          getMessage.call(myObject,"未知",22);//myObject 性别: 未知 age: 22