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[Java教程]JS笔记2


16.javascript中定义对象的几种方式(javascript中没有类的概念,只有对象):

1)基于已有对象扩充其属性和方法:

var object = new Object();
object.name = "zhangsan";
object.sayName = function(name){
  this.name = name;
  alert(this.name);
}
object.sayName("lisi");

2)工厂方式:

//工厂方式创建对象function createObject(){  var object = new Object();  object.username = "zhangsan";  object.password = "123";  object.get = function(){    alert(this.username + ", " + this.password);  }  return object;}var object1 = createObject();var object2 = createObject();object1.get();//带参数的构造方法function createObject(username,password){  var object = new Object();  object.username = username;  object.password = password;  object.get = function(){    alert(this.username + ", " + this.password);  }  return object;}var object1 = createObject("zhangsan","123");object1.get();//让一个函数被多个对象共享,而不是每一个对象拥有一个函数对象function get(){  alert(this.username + ", " + this.password);}function createObject(username,password){  var object = new Object();  object.username = username;  object.password = password;  object.get = get;  return object;}var object1 = createObject("zhangsan","123");var object2 = createObject("lisi","456");object1.get();object2.get();

3)构造函数方式:

function Person(){  //在执行第一行代码前,js引擎会为我们生成一个对象  object.username = "zhangsan";  object.password = "123";  object.getInfo = function(){    alert(this.username + ", " + this.password);  }  //此处有一个隐藏的return语句,用于将之前生成的对象返回}var person = new Person();person.getInfo();//可以在构造对象时传递参数function Person(username,password){  //在执行第一行代码前,js引擎会为我们生成一个对象  object.username = username;  object.password = password;  object.getInfo = function(){    alert(this.username + ", " + this.password);  }  //此处有一个隐藏的return语句,用于将之前生成的对象返回}var person = new Person("zhangsan","123");person.getInfo();

4)原型 ("prototype")方式:

//使用原型 (prototype)方式创建对象function Person(){}Person.prototype.username = "zhangsan";Person.prototype.password= "123";Person.prototype.getInfo = function(){  alert(this.username + ", " + this.password);}var person1 = new Person();var person2 = new Person();person1.username = "lisi";person1.getInfo();person2.getInfo();//function Person(){}Person.prototype.username = new Array();Person.prototype.password= "123";Person.prototype.getInfo = function(){  alert(this.username + ", " + this.password);}var person1 = new Person();var person2 = new Person();person1.username.push("zhangsan");person1.username.push("lisi");person1.password= "456";person1.getInfo();person2.getInfo();//使用原型 + 构造函数方式来定义对象function Person(){  this.username = new Array();  this.password= "123";}Person.prototype.getInfo = function(){  alert(this.username + ", " + this.password);}var person1 = new Person();var person2 = new Person();person1.username.push("zhangsan");person2.username.push("lisi");person1.getInfo();person2.getInfo();

5)动态原型方式:在构造函数中通过标志量让所有对象共享一个方法,而每个对象拥有自己的属性。

function Person(){   this.username = new Array();  this.password= "123";  if(typeof Person.flag == "undefined"){    alert("invoked");      Person.prototype.getInfo = function(){      alert(this.username + ", " + this.password);    }    Person.flag = true;  }}var person1 = new Person();var person2 = new Person();person1.getInfo();person2.getInfo();