-_-#【继承】

javascript prototype 继承

javascript设计模式：继承

function extend(subClass, superClass, methods) {

    var F = function(){};

    F.prototype = superClass.prototype;

    subClass.prototype = new F();

    subClass.prototype.constructor = subClass;

    subClass.superclass = superClass.prototype;

    if (superClass.prototype.constructor == Object.prototype.constructor) {

        superClass.prototype.constructor = superClass;

    }

    for (var p in methods) {

        subClass.prototype[p] = methods[p];

    }

}

 

function SP() {

    this.cls = 'super class'

}

SP.prototype.print = function() {

    console.log(this.cls)

}



function SB() {}

SB.prototype = SP.prototype

SB.prototype.print = function() {

    console.log('changed by subclass')

}



// output: changed by subclass

// SB prototype对象的改变同时影响到了SP，也即此时SB和SP是共享同一个prototype对象

// SB.prototype = new SP() 解决

new SP().print()

 

function SP() {

    this.cls = 'super class'

}

SP.prototype.print = function() {

    console.log(this.cls)

}



function SB() {}

SB.prototype = new SP()

new SB().print() // super class



// 避免在子类SB中获得在父类SP中定义的属性

function F() {}

F.prototype = SP.prototype

SB.prototype = new F()

new SB().print() // undefined

 

function People(name) {

    this.name = name

}

People.prototype.say = function() {

    console.log(this.name)

}

function Baby(name) {

    // 借用构造函数

    Baby.superclass.constructor.call(this, name)

}



Vanilla.extend(Baby, People)



var baby = new Baby('jj')

console.log(baby)