用Ajax读取JSON格式的数据

用Ajax读取JSON格式的数据,也需要先用XMLHttpRequest对象的responseText属性读取,然后再用Function构造返回JSON对象的方法,能过方法创建JSON对象。代码如
下:
1、Client – helloworld.htm

<!--</p> <p>Code highlighting produced by Actipro CodeHighlighter (freeware)</p> <p>http://www.CodeHighlighter.com/</p> <p>--><!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Strict//EN”
“http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd”
>
<html>
<head>
<title>Ajax Hello World</title>
<script type=”text/javascript”>
var xmlHttp;
</script>
</head>
<body>
<div>
<input type=”button” value=”return ajax JSON’s value”
onclick
=”startRequest();” />
</div>
</body>
</html>
2、Server – data.txt

function createXMLHttpRequest(){
if(window.ActiveXObject){
xmlHttp = new ActiveXObject(“Microsoft.XMLHTTP”);
}
else if(window.XMLHttpRequest){
xmlHttp = new XMLHttpRequest();
}
}

function startRequest(){
createXMLHttpRequest();
try{
xmlHttp.onreadystatechange = handleStateChange;
xmlHttp.open(“GET”, “data.txt”, true);
xmlHttp.send(null);
}catch(exception){
alert(“您要访问的资源不存在!”);
}
}

function handleStateChange(){
if(xmlHttp.readyState == 4){
if (xmlHttp.status == 200 || xmlHttp.status == 0){
// 取得返回字符串
var resp = xmlHttp.responseText;
// 构造返回JSON对象的方法
var func = new Function(“return “+resp);
// 得到JSON对象
var json = func( );
// 显示返回结果
alert(“JSON’s value: ” + json.info + “(” + json.version + “v)”);
}
}
}

<!--</p> <p>Code highlighting produced by<br /> Actipro CodeHighlighter<br /> (freeware)</p> <p>http://www.CodeHighlighter.com/</p> <p>-->{
info: “hello world!”,
version: “2.0″
}

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