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HomeWeb Front-endJS TutorialLearn jQuery from scratch (6) AJAX usage in jquery_jquery
Learn jQuery from scratch (6) AJAX usage in jquery_jquery
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May 16, 2016 pm 06:10 PM
ajaxjquery

一.摘要

本系列文章将带您进入jQuery的精彩世界, 其中有很多作者具体的使用经验和解决方案,  即使你会使用jQuery也能在阅读中发现些许秘籍.

本篇文章讲解如何使用jQuery方便快捷的实现Ajax功能.统一所有开发人员使用Ajax的方式.

二.前言

Ajax让用户页面丰富起来, 增强了用户体验. 使用Ajax是所有Web开发的必修课. 虽然Ajax技术并不复杂, 但是实现方式还是会因为每个开发人员的而有所差异.jQuery提供了一系列Ajax函数来帮助我们统一这种差异, 并且让调用Ajax更加简单.

三.原始Ajax与jQuery中的Ajax

首先通过实例, 来看一下jQuery实现Ajax有多简单. 下面是一个使用原始Ajax的示例:

<SPAN class=kwrd><!</SPAN><SPAN class=html>DOCTYPE</SPAN> <SPAN class=attr>html</SPAN> <SPAN class=attr>PUBLIC</SPAN> <SPAN class=kwrd>"-//W3C//DTD XHTML 1.0 Transitional//EN"</SPAN> <SPAN class=kwrd>"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"</SPAN><SPAN class=kwrd>></SPAN>
<SPAN class=kwrd><</SPAN><SPAN class=html>html</SPAN> <SPAN class=attr>xmlns</SPAN><SPAN class=kwrd>="http://www.w3.org/1999/xhtml"</SPAN><SPAN class=kwrd>></SPAN>
<SPAN class=kwrd><</SPAN><SPAN class=html>head</SPAN><SPAN class=kwrd>></SPAN>
  <SPAN class=kwrd><</SPAN><SPAN class=html>title</SPAN><SPAN class=kwrd>></SPAN>jQuery Ajax<SPAN class=kwrd></</SPAN><SPAN class=html>title</SPAN><SPAN class=kwrd>></SPAN>
  <script type=<SPAN class=str>"text/javascript"</SPAN>>
    $(<SPAN class=kwrd>function</SPAN>()
    {
      <SPAN class=kwrd>var</SPAN> xhr = <SPAN class=kwrd>new</SPAN> AjaxXmlHttpRequest();
      $(<SPAN class=str>"#btnAjaxOld"</SPAN>).click(<SPAN class=kwrd>function</SPAN>(<SPAN class=kwrd>event</SPAN>)
      {
        <SPAN class=kwrd>var</SPAN> xhr = <SPAN class=kwrd>new</SPAN> AjaxXmlHttpRequest();
        xhr.onreadystatechange = <SPAN class=kwrd>function</SPAN>()
        {
          <SPAN class=kwrd>if</SPAN> (xhr.readyState == 4)
          {
            document.getElementById(<SPAN class=str>"divResult"</SPAN>).innerHTML = xhr.responseText;
          }
        }
        xhr.open(<SPAN class=str>"GET"</SPAN>, <SPAN class=str>"data/AjaxGetCityInfo.aspx?resultType=html"</SPAN>, <SPAN class=kwrd>true</SPAN>);
        xhr.send(<SPAN class=kwrd>null</SPAN>);
      });
    })

    <SPAN class=rem>//跨浏览器获取XmlHttpRequest对象</SPAN>
    <SPAN class=kwrd>function</SPAN> AjaxXmlHttpRequest()
    {
      <SPAN class=kwrd>var</SPAN> xmlHttp;
      <SPAN class=kwrd>try</SPAN>
      {
        <SPAN class=rem>// Firefox, Opera 8.0+, Safari</SPAN>
        xmlHttp = <SPAN class=kwrd>new</SPAN> XMLHttpRequest();
      }
      <SPAN class=kwrd>catch</SPAN> (e)
      {

        <SPAN class=rem>// Internet Explorer</SPAN>
        <SPAN class=kwrd>try</SPAN>
        {
          xmlHttp = <SPAN class=kwrd>new</SPAN> ActiveXObject(<SPAN class=str>"Msxml2.XMLHTTP"</SPAN>);
        }
        <SPAN class=kwrd>catch</SPAN> (e)
        {

          <SPAN class=kwrd>try</SPAN>
          {
            xmlHttp = <SPAN class=kwrd>new</SPAN> ActiveXObject(<SPAN class=str>"Microsoft.XMLHTTP"</SPAN>);
          }
          <SPAN class=kwrd>catch</SPAN> (e)
          {
            alert(<SPAN class=str>"您的浏览器不支持AJAX！"</SPAN>);
            <SPAN class=kwrd>return</SPAN> <SPAN class=kwrd>false</SPAN>;
          }
        }
      }
      <SPAN class=kwrd>return</SPAN> xmlHttp;
    }    
  <SPAN class=kwrd></</SPAN><SPAN class=html>script</SPAN><SPAN class=kwrd>></SPAN>

<SPAN class=kwrd></</SPAN><SPAN class=html>head</SPAN><SPAN class=kwrd>></SPAN>
<SPAN class=kwrd><</SPAN><SPAN class=html>body</SPAN><SPAN class=kwrd>></SPAN>  
  <SPAN class=kwrd><</SPAN><SPAN class=html>button</SPAN> <SPAN class=attr>id</SPAN><SPAN class=kwrd>="btnAjaxOld"</SPAN><SPAN class=kwrd>></SPAN>原始Ajax调用<SPAN class=kwrd></</SPAN><SPAN class=html>button</SPAN><SPAN class=kwrd>><</SPAN><SPAN class=html>br</SPAN> <SPAN class=kwrd>/></SPAN>
  <SPAN class=kwrd><</SPAN><SPAN class=html>br</SPAN> <SPAN class=kwrd>/></SPAN>
  <SPAN class=kwrd><</SPAN><SPAN class=html>div</SPAN> <SPAN class=attr>id</SPAN><SPAN class=kwrd>="divResult"</SPAN><SPAN class=kwrd>></</SPAN><SPAN class=html>div</SPAN><SPAN class=kwrd>></SPAN>
<SPAN class=kwrd></</SPAN><SPAN class=html>body</SPAN><SPAN class=kwrd>></SPAN>
<SPAN class=kwrd></</SPAN><SPAN class=html>html</SPAN><SPAN class=kwrd>></SPAN>

上面的实例中, data/AjaxGetCityInfo.aspx?resultType=html 地址会返回一段HTML代码.

使用原始Ajax, 我们需要做较多的事情, 比如创建XmlHttpRequest对象,  判断请求状态, 编写回调函数等.

而用jQuery的Load方法, 只需要一句话:

$(<SPAN class=str>"#divResult"</SPAN>).load(<SPAN class=str>"data/AjaxGetCityInfo.aspx"</SPAN>, { <SPAN class=str>"resultType"</SPAN>: <SPAN class=str>"html"</SPAN> });

 

曾经我是一个原始Ajax的绝对拥护者, 甚至摒弃微软的Asp.net Ajax, 因为我想要最高的代码灵活度. 使用原始Ajax让我感觉完成自己的工作更加轻松, 即使多写了一些代码. 但是当我去翻看别人的Ajax代码并且尝试修改的时候, 我改变了我的看法--我们的代码到处分布着创建XmlHttpRequest方法的函数, 或者某些Ajax程序逻辑性和结构性很差, 很难看懂.

我们可以将通用方法放到一个js文件中, 然后告诉大家"嘿伙伴们, 都来用这个js中的方法". 但是在某些时候有些新来的外包人员并不知道有这个js文件的存在. 而且其实这个通用的js就是一个公共的脚本类库,  我相信没有人会觉得自己开发一个类库会比jQuery更好!

所以我放弃了制造轮子的计划,  大家都使用jQuery编写Ajax相关的方法就可以解决各种差异性问题, 并且让工作更有效率.

现在只是用jQuery的Ajax函数, 我的页面变得简洁了: 

DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
  <title>jQuery Ajaxtitle>
  <script type="text/javascript" src="scripts/jquery-1.3.2-vsdoc2.js">script>
  
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