javascript继承

拷贝继承

　　 function Foo(){   //父类
        this.name = 'hello';
    }
    Foo.prototype.showName = function(){
        console.log(this.name);
    };
    function Bar(){   //子类
        Foo.call(this);
        this.age = 20;
        this.name = 'hi'
    }
    extend(Bar,Foo);
    Bar.prototype.showAge = function(){
        console.log(this.age);
    };
    function extend(subs,sups){
        for(var attr in sups.prototype){
            subs.prototype[attr] = sups.prototype[attr];
        }
    }
    var obj1 = new Foo();
    var obj2 = new Bar();
    console.log(obj1);
    console.log(obj2);
    obj2.showName()

类式继承

    function Foo(){
        this.name = 'hello';
    }
    Foo.prototype.showName = function(){
        console.log(this.name);
    };
    function Bar(){
        Foo.call(this);
        this.age = 20;
    }
    extend(Bar,Foo);
    Bar.prototype.showAge = function(){
        console.log(this.age);
    };
    function extend(subs,sups){
        var F = function(){};
        F.prototype = sups.prototype;
        subs.prototype = new F();
    // constructor 找对应的构造函数;
        subs.prototype.constructor = subs;
    }
    var obj1 = new Foo();
    var obj2 = new Bar();
    console.log(obj1);
    console.log(obj2);

非构造函数拷贝继承

    var foo = {
        name : 'hello'
    };
    foo.showName = function(){
        console.log(this.name)
    }
    var bar = extend(foo);
    function extend(sups){
        var result = {};
        for(var attr in sups){
            result[attr] = sups[attr];
        }
        return result;
    }
    console.log(bar);
    bar.name = 'hi';
    console.log(bar);
    console.log(foo);
    bar.showName();

原型链形式

　　 var foo = {
        name : 'hello',
        showName: function(){
            console.log(this.name)
        }
    };
    var bar = extend(foo);
    function extend(sups){
        function F() {}
        F.prototype = sups;
　　　　return new F();
    }
    console.log(bar);
    bar.name = 'hi';
    console.log(bar);
    console.log(foo);
    bar.showName()