javascript的几种定义对象的方式

2016-02-23 13:53:54
js中定义对象的几种方式
 
1. 基于已有对象扩充其对象和方法(只适合于临时的生成一个对象):
  var obj = new Object();
  obj.name="userObject";
  obj.printName = function(name){
  this.name = name;
  alert(this.name);
  }
  obj.printName("newUserObject");
2.工厂方式创建对象(每次创建一个object后,其中对应的方法(本例中是get)也被创建一次,方法不能被所创建的所有对象(本例中是obj1和obj2)共享):
  a.
  function createObject(){
  var obj = new Object();
  obj.name="userObject";
  obj.password = "12345";
  obj.get = function(){
   alert(this.name + ", " + this.password);
  }
  return obj;
  }
  var obj1 = createObject();
  var obj2 = createObject();
  obj1.get();
  obj2.get();
  b.带参数的构造方法:
  function createObject(username,password){
  var obj = new Object();
  obj.username = username;
  obj.password = password;
  obj.get = function(){
  alert(this.username + ", " + this.password);
  }
  return obj;
  }
  var obj1 = createObject("zhangsan","123456");
  obj1.get();
  c.让函数被多个创建的对象所共享,而不是每一个对象都创建一个相同的函数(缺点:对象定义本身和方法分离了):
  function get(){
  alert(this.username + ", " + this.password);
  }
  function createObject(username,password){
  var obj = new Object();
  obj.username = username;
  obj.password = password;
  obj.get = get;
  return obj;
  }
  var obj1 = createObject("zhangsan","123456");
  var obj2 = createObject("lisi","54321");
  obj1.get();
  obj2.get();
3.构造函数方式:
  a.
  function Person(){
  this.username = "zhangsan";
  this.password = "123";
  this.getInfo = function(){
  alert(this.username + ", " + this.password);
  }
  }
  var person = new Person();
  person.getInfo();
  b.可以在构造函数是传递参数:
  function Person(username,password){
  this.username = username;
  this.password = password;
  this.getInfo = function(){
  alert(this.username + ", " + this.password);
  }
  }
  var person = new Person("zhangsan","123");
  person.getInfo();
4.使用原型(prototype)方式创建对象:
  优点:创建的多个对象共享同一个方法(getInfo)
  缺点:创建的多个对象在共享同一个方法的同时也共享了同样的属性(username,password),实际开发中这样儿是
  不行的,必须是多个对象都要有自己的属性。
  采用该方式创建对象通常是用来扩展已有对象的某一个方法。
  a.
  function Person(){}
  Person.prototype.username = "zhangsan";
  Person.prototype.password = "123";
  Person.prototype.getInfo = function(){
  alert(this.username + ", " + this.password);
  }
  var person = new Person();
  var person2 = new Person();
  person.username = "lisi";
  person.getInfo();
  person2.getInfo();
  b.如果使用原型方式创建对象,那么生成的所有对象将会共享原型中的属性,这样儿一个对象改变了该属性也会反应到其他的对象上:
  function Person(){}
  Person.prototype.username = new Array(0;
  Person.prototype.password = "123";
  Person.prototype.getInfo = function(){
  alert(this.username + ", " + this.password);
  }
  var person = new Person();
  var person2 = new Person();
  person.username.push("zhangsan");
  person.username.push("lisi");
  person.password = "456";
  person.getInfo();
  person2.getInfo();
  c.使用原型和构造函数方式来创建对象:
  function Person(){
  this.username = new Array();
  this.password = "123"
  }
  Person.prototype.getInfo = function(){
  alert(this.username + ", " + this.password);
  }
  var person = new Person();
  var person2 = new Person();
  person.username.push("zhangsan");
  person.username.push("lisi");
  person.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 Persion(){
  this.username = "zhangsan";
  this.password = "123";
  if(typeof Person.flag == "undefined"){
  Person.prototype.getInfo = function(){
  alert(this.username + ", " + this.password);
  }
  Person.flag = true;
  }
  }
  var p = new Person();
  var p2 = new Person();
  p.getInfo();
  p2.getInfo();
 
6.对象的创建--JSON
var obj = {
eye : 'blue';
height : 1.72;
hair : 'long';
 
eat : function(){
alert("my hair is "+this.hair);
}
 
}

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