轻松掌握XMLHttpRequest对象
最通用的定义为:XmlHttp是一套可以在Javascript、VbScript、Jscript等脚本语言中通过http协议传送或从接收XML及其他数据的一套API。XmlHttp最大的用处是可以更新网页的部分内容而不需要刷新整个页面。
来自MSDN的解释:XmlHttp提供客户端同http服务器通讯的协议。客户端可以通过XmlHttp对象(MSXML2.XMLHTTP.3.0)向http服务器发送请求并使用微软XML文档对象模型Microsoft® XML Document Object Model (DOM)处理回应。 现在的绝对多数浏览器都增加了对XmlHttp的支持,IE中使用ActiveXObject方式创建XmlHttp对象,其他浏览器如:Firefox、Opera等通过window.XMLHttpRequest来创建xmlhttp对象。
XmlHttp对象的属性:
XmlHttp对象的方法:
如何发送一个简单的请求?
最简单的请求是,不以查询参数或提交表单的方式向服务器发送任何信息.使用XmlHttpRequest对象发送请求的基本步骤:
● 为得到XmlHttpRequest对象实例的一个引用,可以创建一个新的XmlHttpRequest的实例。
● 告诉XmlHttpRequest对象,那个函数回处理XmlHttpRequest对象的状态的改变.为此要把对象的
onreadystatechange属性设置为指向JavaScript的指针.
● 指定请求属性.XmlHttpRequest对象的Open()方法会指定将发送的请求.
● 将请求发送给服务器.XmlHttpRequest对象的send()方法将请求发送到目标资源.
XmlHttpRequest实例分析
我想大家都知道,要想使用一不对象首先我门得做什么?是不是必须先创建一个对象吧.比如C#和Java里用new来实例对象.那么我门现在要使用XmlHttp对象是不是也应该先创建一个XmlHttp对象呢?这是毫无疑问的!那么下面我们来看看在客户端怎么创建一个XmlHttp对象,并使用这个对象向服务端发送Http请求,然后处理服务器返回的响应信息.
1.创建一个XmlHttp对象(在这里我以一个无刷新做加法运算的实例 )
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2.定义发送请求的方法
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3.定义回调函数,用于处理服务端返回的信息
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现在我门就可以调用AddNumber()这个方法向服务端发送请求来做一个无刷新的加法运算了.
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这个实例虽然很简单.我之所以用这个实例主要是给大家介绍XmlHttp对象的处理过程.文章后面我把项目文件提供下载.
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上面把JS写到页面中了,在实际的项目开发中是不推荐这样做的,最好把JS代码都定义到一个JS文件类.我这里有一份XmlHttpRequest对象的JS(网上下载的),把相关的方法基本都写全了.下面我门来看看怎么使用这个外部JS文件来发送异步请求及响应.
我门先来看看这个JS文件的详细定义:
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一个简单的Hello实例:
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关于XmlHttpRequest对象就介绍到这里,更多更详细的内容请大家查看相关资料.
欢迎拍砖指正,不甚感激!
本文实例源代码下载
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