javascript对象的创建 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: [html] view plain copy print? 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 [html] view plain copy print? //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: [html] view plain copy print? 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();
让一个函数对象被多个对象所共享,而不是每一个对象拥有一个函数对象。 [html] view plain copy print? 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 object = createObject('zhangsan', '123'); var object2 = createObject('lisi', '456'); object.get(); object2.get();
3)构造函数方式 [html] view plain copy print? function Person() { //在执行第一行代码前,js引擎会为我们生成一个对象 this.username = 'zhangsan'; this.password = '123'; this.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 [html] view plain copy print? 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)原型(“prototype”)方式 [html] view plain copy print? //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 person = new Person(); var person2 = new Person(); person.username = 'lisi'; person.getInfo(); person2.getInfo(); */
[html] view plain copy print? function Person() { } Person.prototype.username = new Array(); 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();
如果使用原型方式对象,那么生成的所有对象会共享原型中的属性,这样一个对象改变了该属性也会反应到其他对象当中。 单纯使用原型方式定义对象无法在构造函数中为属性赋初值,只能在对象生成后再去改变属性值。 使用原型+构造函数方式来定义对象,对象之间的属性互不干扰,各 个对象间共享同一个方法 [html] view plain copy print? //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 p = new Person(); var p2 = new Person(); p.username.push('zhangsan'); p2.username.push('lisi'); p.getInfo(); p2.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。 [html] view plain copy print? function Person() { this.username = 'zhangsan'; this.password = '123'; if(typeof Person.flag == 'undefined') { alert('invoked'); Person.prototype.getInfo = function() { alert(this.username + ', ' + this.password); } Person.flag = true; } } var p = new Person(); var p2 = new Person(); p.getInfo(); p2.getInfo();
JavaScript中的继承。 1) 对象冒充 [html] view plain copy print? //继承第一种方式:对象冒充 function Parent(username) { this.username = username; this.sayHello = function() { alert(this.username); } } function Child(username, password) { //下面三行代码是最关键的代码 this.method = Parent; this.method(username); delete this.method; this.password = password; this.sayWorld = function() { alert(this.password); } } var parent = new Parent('zhangsan'); var child = new Child('lisi', '1234'); parent.sayHello(); child.sayHello(); child.sayWorld();
2) call方法方式。 call方法是Function对象中的方法,因此我们定义的每个函数都拥有该方法。可以通过函数名来调用call方法,call方法的第一个参数会被传递给函数中的this,从第2个参数开始,逐一赋值给函数中的参数。
[html] view plain copy print? //使用call方式实现对象的继承function Parent(username) { this.username = username; this.sayHello = function() { alert(this.username); } }function Child(username, password) { Parent.call(this, username); this.password = password; this.sayWorld = function() { alert(this.password); } }var parent = new Parent('zhangsan');var child = new Child('lisi', '123');parent.sayHello();child.sayHello(); child.sayWorld(); <> style='font-size:18px;'><> style='color:#000000;'>
3) apply方法方式 [html] view plain copy print? //使用apply方法实现对象继承 function Parent(username) { this.username = username; this.sayHello = function() { alert(this.username); } } function Child(username, password) { Parent.apply(this, new Array(username)); this.password = password; this.sayWorld = function() { alert(this.password); } } var parent = new Parent('zhangsan'); var child = new Child('lisi', '123'); parent.sayHello(); child.sayHello(); child.sayWorld();
4)原型链方式(无法给构造函数传参数) [html] view plain copy print? //使用原型链(prototype chain)方式实现对象继承 function Parent() { } Parent.prototype.hello = 'hello'; Parent.prototype.sayHello = function() { alert(this.hello); } function Child() { } Child.prototype = new Parent(); Child.prototype.world = 'world'; Child.prototype.sayWorld = function() { alert(this.world); } var child = new Child(); child.sayHello(); child.sayWorld();
5)混合方式(推荐)
[html] view plain copy print? //使用混合方式实现对象继承(推荐) function Parent(hello) { this.hello = hello; } Parent.prototype.sayHello = function() { alert(this.hello); } function Child(hello, world) { Parent.call(this, hello); this.world = world; } Child.prototype = new Parent(); Child.prototype.sayWorld = function() { alert(this.world); } var child = new Child('hello', 'world'); child.sayHello(); child.sayWorld();
|