function Shape() {    this.name = ‘shape‘;    this.toString = function(){        return this.name;    }}function TwoDshape () {    this.name = ‘2D shape‘;}function Triangle (side,height) {    this.name = ‘Triangle‘;    this.side = side;    this.height = height;    this.getArea = function () {        return this.side * this.height / 2;    }}TwoDshape.prototype = new Shape();Triangle.prototype = new TwoDshape();   //用new新建对象实体，并赋值覆盖该对象的原型TwoDshape.prototype.constructor = TwoDshape;Triangle.prototype.constructor = Triangle; var my = new Triangle(5,10); my.getArea();　　 　　　　//25console.log(my.toString());//继承的方法，具体步骤（遍历my对象属性没有找到，接着查看my.__proto__所指向的对象，即new TwoDshape()创建的实体，//依然没找到，又继续查找该实体的__proto__所指向的对象，即new Shape()所创建的实体，找到toString方法，并在my对象中被调用，this指向my）//通过instanceof操作符，我们可以验证my对象同时是上面三个构造器的实例my instanceof Shape；    　　    //truemy instanceof  TwoDShape；     //truemy instanceof Triangle；      //true

//我们也可以用其他两个构造器来创建对象，用new TwoDshape()所创建的对象也可以获得继承自Shape()的toString()方法
var td = new TwoDshape();
td.constructor === TwoDshape;   //true;
td.toString();　　　　　　　　　　// 2D shape

var s = new Shape();
s.constructor === shape;　　　　// true;

function Shape(){this.name=‘shape‘}//使用new Shape()新建对象，每个实体都有全新的属性并占用独立空间function Shape(){};Shape.prototype.name=‘shape‘;//属性移到原型后，使用new新建对象时，不再含自己独立的这个属性

Triangle.prototype=Shape.prototype;//减少继承方法的查询步骤Triangle.prototype.name=‘Triangle‘;//修改子对象原型后父对象原型也随即被改，即再new Shape()新建对象时，新对象name为‘Triangl

function Shape() {}Shape.prototype.name = "shape";Shape.prototype.toString = function () {    return this.name;}function TwoDshape() {}var F = function () {};F.prototype = Shape.prototype;TwoDshape.prototype = new F();TwoDshape.prototype.constructor = TwoDshape;TwoDshape.prototype.name = ‘2D shape‘;function Triangle(side, height) {    this.side = side;    this.height = height;}var F = function () {};F.prototype = TwoDshape.prototype;Triangle.prototype = new F();Triangle.prototype.constructor = Triangle;Triangle.prototype.name = ‘Triangle‘;Triangle.prototype.getArea = function () {    return this.side * this.height / 2;}var my = new Triangle (5,10);alert(my.getArea());

//通过这种方法，我们仍然能保持住原型链
my._proto_ === Triangle.prototype;　　　　　　　　　　　　  //true
my._proto_.constructor === Triangle;　　　　　　　　　　　　//true
my._proto_._proto_ === TwoDshape.prototypr;　　　　　　　　//true
my._proto_._proto_._proto_.constructor === Shape;_　　　　//true

//并且父对象的属性不会被子对象覆盖：
var s = new Shape();
s.name;    // shape

//calling toString()
"I am a" + new TwoDshape();　　　　　//I am a 2D shape　　　

function Shape(){}Shape.prototype.name=‘shape‘;Shape.prototype.toString=function(){　　var const = this.constructor;
　　return const.uber
　　　　　? this.const.uber.toString() + ‘,‘ + this.name
　　　　　： this.name;
}function TwoDShape(){}var F=function(){}F.prototype=Shape.prototype;TwoDShape.prototype=new F();TwoDShape.prototype.constructor=TwoDShape;TwoDShape.uber=Shape.prototype;TwoDShape.prototype.name=‘2D shape‘;function Triangle(side,height){  this.side=side;  this.height=height;}var F=function(){}F.prototype=TwoDShape.prototype;Triangle.prototype=new F();Triangle.prototype.constructor=Triangle;Triangle.uber=TwoDShape.prototype;Triangle.prototype.name=‘triangle‘;Triangle.prototype.getArea=function(){return this.side*this.height/2};var my=new Triangle(5,10)console.log(my.toString());//shape,2D shape,triangle