js继承

组合式继承

function super(name){
    this.name=name;
    this.colors=["red","blue","green"]
}
super.prototype.sayName=function(){
    console.log(this.name);
};

function sub(name,number){
    // 继承属性
    super.call(this,name);
    this.number=number;
}
//继承方法
sub.prototype=new super();//类似继承，引用，子类改变会影响父类
sub.prototype.sayNum=function(){
    console.log(this.number);
}

var instance1=new sub("cherry",23);
instance1.colors.push("magenta");
console.log(instance1.colors);//"red,blue,green,magenta"
instance1.sayName();//"cherry"
instance1.sayNum();//23

var instance2=new sub("blueberry",25);
console.log(instance2.colors);//"red blue,green"
instance2.sayName();//"blueberry"
instance2.sayNum();//25

//融合了原型链和构造函数的优点

 寄生组合式继承

function super(name){
    this.name=name;
    this.colors=["red","blue","green"];
}

super.prototype.sayName=function(){
    console.log(this.name);
}

function sub(name,age){
    super.call(this,name);
    this.age=age;
}

//
function inheritPrototype(sub,super){
    var prototype=object(super);//创建super原型的一个副本
    prototype.constructor=sub;//为创建的副本添加constructor属性
    //从而弥补因原型重写而失去的默认的constructor属性
    sub.prototype=prototype;//将创建的副本赋值给子类原型
    //即可调用inheritPrototype()替换组合继承中为子类原型赋值的语句
}
inheritPrototype(sub,super);

sub.prototype.sayAge=function(){
    console.log(this.age);
}

原型链继承即将一个对象的实例赋值给另一对象的原型实现继承

拷贝继承

 修复类似继承：借助中间类实现

    var a={
                name:'roy'
            }
            var b=cloneobj(a);
            
            b.name='richard';
            alert(a.name);
            alert(b.name);
            function cloneobj(obj){//原型继承
                var f=function(){};//中间子类
                f.prototype=obj;
                return new f();
            }
            
            
            //拷贝继承：比较通用的方式，有无new都可以用
            //类式继承：new 构造函数
            //原型继承：无new对象