创建对象的几种方式：

字面量创建

var o ={a:1,b:2};原型链如下：o ---> Object.prototype --->null继承的属性比如：hasOwnPropertyvar a = ["i", "like", "you"];原型链如下：a ---> Array.prototype ---> Object.prototype ---> null继承的属性比如：indexOf,forEachvar f = function(){return 2;}原型链如下：f ---> Function.prototype ---> Object.prototype ---> null继承的属性比如：call,bind,apply

使用构造器创建对象

构造器就是一个普通的函数function Graph(){    this.vertexes = [];    this.edges = [];}Graph.prototype = {    addVertex: function(v){        this.vertexes.push(v);    }};var g = new Graph();// g是生成的对象，它的自身属性有'vertexes','edges',// 在g被实例化时，g.[[prototype]]指向了Graph.prototype

使用Object.create创建对象

var a = {a:1};// a ---> Object.prototype ---> nullvar b = Object.create(a);//b ---> a ---> Object.prototype --->nullvar c = Object.create(b);//c ---> b ---> a ---> Object.prototype --->nullvar d = Object.create(null);//d ---> nullconsole.log(d.hasOwnProperty); // undefined,因为d没有继承Object.prototype

使用class关键字

‘use strict’class Polygon {    constructor(height,width){        this.height = height;        this.width = width;    }}class Square extends Polygon {    constructor(sideLength){        super(sideLength, sideLength);    }    get area() {        return this.height * this.width;    }    set sideLength(newLength) {        this.height = newLength;        this.wdith = newLength;    }}var square = new Square(2);