JavaScript：对象
一、理解对象
var person = {}Object.defineProperty(person,'name',{writable:false,value : 'Nike'})console.log(person.name);person.name = 'Gray';console.log(person.name);console.log(person);
二、创建对象
2.1、工厂模式
function Person(name,age,job){var obj = new Object()obj.name = nameobj.age = ageobj.job = jobobj.sayName = function(){console.log(this.name);}return obj;}var person = Person('Loly',13,'程序员');person.sayName() //Loly
2.2、构造函数模式
function Person(name,age,job) {this.name = name;this.age = age;this.job = job;this.sayName = function(){console.log(this.name);}}
创建Person的新实例，必须使用new操作符
1、创建一个新对象
2、将构造函数的作用域赋给新对象
3、执行构造函数中的代码
4、返回新对象
var person = new Person('Ahad',23,'sad')person.sayName()console.log(person.constructor == Person);//trueconsole.log(person instanceof Object);//trueconsole.log(person instanceof Person);//true
2.3、原型模式
function Person(){}Person.prototype.name = "Mike";Person.prototype.age = 12;Person.prototype.sayName = function(){console.log(this.name);}var person = new Person();var otherperson = new Person();console.log(person.sayName == otherperson.sayName)//true 属性和方法是绑定在原型上的，是可共享的
//getPrototypeOf返回的对象是这个对象的原型Object.getPrototypeOf(person);//Person//isPrototypeOf（）方法：确定对象之间是否存在原型和实例关系Person.prototype.isPrototypeOf(person);//true//hasOwnProperty():检测一个属性是否存在于实例中person.name = 'Gery'console.log(person.hasOwnProperty('name'));//true 此时name来自实例delete person.nameconsole.log(person.hasOwnProperty('name'));//false 此时name来自原型,实例没有属于自己的name属性
//原型与in操作符( 无论该属性存在于实例还是原型 )console.log('name' in person);//true name来自原型person.name = 'Gery'console.log('name' in person);//true name来自实例
//hasOwnProperty和in操作符合作判断属性是原型的还是实例对象的function hasPrototypeProperty(object,name){return !object.hasOwnProperty(name) && (name in object);}function Per(){}Per.prototype.name = 'Mike'var per = new Per();console.log(hasPrototypeProperty(per,'name'));//true per.hasOwnProperty(name)是0，取反为1，1&&1=1，name属于原型per.name = 'Dike'console.log(hasPrototypeProperty(per,'name'));//false per.hasOwnProperty(name)是1，取反为0，1&&0=0，name属于实例
//Object.keys()返回一个包含所有可枚举属性的字符串数组Object.keys(Person.prototype);//['name', 'age', 'sayName']Object.keys(person); //['name', 'age', 'sayName']
//Object.getOwnPropertyNames返回所有实例属性Object.getOwnPropertyNames(Person.prototype); //['constructor', 'name', 'age', 'sayName']Object.getOwnPropertyNames(person); //['name', 'age', 'sayName']
//更简单的原型语法function People(){}People.prototype = {// constructor:People,name:'KKK',age:19,job:'boss',sayName:function(){console.log(this.name);}}var friend = new People()console.log(friend.constructor);//ƒ Object() //此时的constructor不再指向People，而是指向Object构造函数，如果constructor很重要，可以设置constructor:People，如上所示，此时[[Enumerble]]特性被设置为true//重设构造函数，只适用于ECMAScript5兼容的浏览器Object.defineProperty(People.prototype,'constructor',{enumerable:false,value:People})console.log(friend.constructor); //f People(){}
//原型的动态性//1、function People(){}People.prototype = {constructor:People,name:'KKK',age:19,job:'boss',sayName:function(){console.log(this.name);}}var friend = new People()//创建People.prototype.sayNo = function(){console.log("NoNoNo");}friend.sayNo()//NoNoNofunction People1(){//1}var friend1 = new People1();//创建实例 引用的是原来的原型，此时创建的friend实例没有sayName方法People1.prototype = {//2、重写了原型constructor:People1,name:'KKK',age:19,job:'boss',sayName:function(){console.log(this.name);}}var friend2 = new People1(); //创建实例 引用的是重写后的原型，此时创建的friend2实例有sayName方法friend1.sayName() //error 报错friend2.sayName() //KKK
//原型对象问题People.prototype.friends = ['a','b']var friend3 = new People()var friend4 = new People()friend3.friends.push('c') //friend3修改了原型中共享的friends属性，这时friend4指向的同一个friends也更改了console.log(friend3.friends);//['a', 'b', 'c']console.log(friend4.friends);//['a', 'b', 'c']
2.4、结合使用构造函数模式和原型模式
function Unite(name,age,job){this.name = namethis.age = agethis.job = jobthis.friends = ['She','He']}Unite.prototype = {constructor:Unite,sayName:function(){console.log(this.name);}}var unite1 = new Unite('YY',18,'cooker')var unite2 = new Unite('ZZ',21,'painter')unite1.friends.push('It') //修改的是实例的属性console.log(unite1.friends);//['She', 'He', 'It']console.log(unite2.friends);//['She', 'He']console.log(unite1.friends == unite2.friends);//falseconsole.log(unite1.sayName == unite2.sayName);//true
2.5、动态原型模式
(不能使用对象字面量重写原型)
function DynamicPrototype(name,age){this.name = namethis.age = age//方法if(typeof this.sayName != "function"){DynamicPrototype.sayName = function(){console.log(this.name);}}}console.log(DynamicPrototype.prototype);var dp = new DynamicPrototype('SS',32)
2.6、寄生构造函数模式
function ParasiticModels(name,age,job){var obj = new Object()obj.name = nameobj.age = ageobj.job = jobobj.sayName = function(){console.log(this.name);}return obj;}var parasiticModels = new ParasiticModels('寄生',13,'程序员');parasiticModels.sayName() //Loly
2.7、稳妥构造函数模式
创建对象的实例方法时不引用this,不使用new操作符调用构造函数
function SafeModel(name,age,job){var obj = new Object();//可以在这里定义私有变量和函数//添加方法obj.sayName = function(){console.log(name);};return obj;}var safeModel = SafeModel('稳妥',21,'boss')safeModel.sayName() //只能访问到sayName()方法，无法访问其他数据成员
