一、创建对象的几种办法

// 1、字面量var o1 = {name:'lihaixing'};var o11 = new Object({name:'lihaixing'});// 2、构造函数var M = function(){this.name='haixing'};var o2 = new M();// 3、基于原型var P = {name:'haixing'};var o3 = Object.create(P);var o33 = Object.create(null);

二、原型链

var M = function () {    this.name = 'haixing';    // return {}};var o2 = new M();console.log(M.prototype.constructor === M); // trueconsole.log(M.prototype === o2.__proto__); // trueconsole.log(M.prototype.__proto__ === Object.prototype); // trueconsole.log(M.__proto__ === Function.prototype); // trueconsole.log(Object.prototype.__proto__===null); // trueconsole.log(o2 instanceof M); // true console.log(M.prototype instanceof Object); // true console.log(o2 instanceof Object); // true  只有一条链上就能够

三、继承

1、借助构造函数实现继承

function Parent1 () {    this.name = 'parent1'    this.play = [1, 2, 3]}function Child1 () {    Parent1.call(this)    this.type = 'child1'}

毛病：只是将Parents的this指向了Child1的实例，但Parents.prototype中的属性却无奈继承下来

// 测试Parent1.prototype.say=function(){    console.log('Parent1 prototye')}var son1 = new Child1();son1.say(); // Uncaught TypeError: son1.say is not a function

2、借助原型链实现继承

function Parent2 () {    this.name = 'parent2'    this.play = [1, 2, 3]}function Child2 () {    this.type = 'child2'}Child2.prototype = new Parent2();

毛病：尽管实现了继承，然而父类实例后的数据却是共用得，导致某个实例扭转父亲的数据，其它儿子也就共享了

// 测试Parent2.prototype.say = function () {    console.log('say')}var son2 = new Child2();var son22 = new Child2();son2.say(); // sayson2.play.push(4);console.log(son22.play); // [ 1, 2, 3, 4 ]

3、联合以上两种办法实现继承

function Parent3 () {    this.name = 'parent3'    this.play = [1, 2, 3]}function Child3 () {    Parent3.call(this)    this.type = 'child3'}Child3.prototype = new Parent3()

毛病：尽管解决了各自的毛病，但父类执行了两次，并且父类和子类还有雷同的属性

4、父类的原型赋值给子类

function Parent4 () {    this.name = 'parent4'    this.play = [1, 2, 3]}function Child4 () {    Parent4.call(this)    this.type = 'child3'}Child4.prototype = Parent4.prototype

毛病:

  • Child4.prototype = Parent4.prototype 使得Child4和Parent4实例得结构器都指向了Parent4, 这显著不是咱们想要的，咱们心愿Child4.prototype.contructor依然是Child4
  • 有人想到Child4.prototype.constructor = Child4将结构器再改回来，然而这样Parent4.prototype.contructor成了Child4也不妥呀
// 测试var son4 = new Child4();// instanceof 取决于由谁创立的，同一条线都可console.log(son4 instanceof Child4, son4 instanceof Parent4) // true true// 结构器在原型上呢，取决于Child4.prototype.contructorconsole.log(Child4.prototype.constructor, Parent4.prototype.constructor) // Parent4 Parent4

5、基于object.create

function Parent5 () {    this.name = 'parent5'    this.play = [1, 2, 3]}function Child5 () {    Parent5.call(this)    this.type = 'child5'}Child5.prototype = Object.create(Parent5.prototype);Child5.prototype.constructor = Child5;

最初一个比拟完满，不说了

var son5 = new Child5();console.log(son5 instanceof Child5, son5 instanceof Parent5); // true trueconsole.log(Child5.prototype.constructor,Parent5.prototype.constructor); // Child5 Parent5