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使用 XMLHttpRequest 实现 Ajax 三:取回 Json 数据

2010-06-27 18:01 1276 查看
首先建立json.txt文件

{
"programmers": [
{ "firstName": "Brett", "lastName":"McLaughlin", "email": "brett@newInstance.com" },
{ "firstName": "Jason", "lastName":"Hunter", "email": "jason@servlets.com" },
{ "firstName": "Elliotte", "lastName":"Harold", "email": "elharo@macfaq.com" }
],
"authors": [
{ "firstName": "Isaac", "lastName": "Asimov", "genre": "science fiction" },
{ "firstName": "Tad", "lastName": "Williams", "genre": "fantasy" },
{ "firstName": "Frank", "lastName": "Peretti", "genre": "christian fiction" }
],
"musicians": [
{ "firstName": "Eric", "lastName": "Clapton", "instrument": "guitar" },
{ "firstName": "Sergei", "lastName": "Rachmaninoff", "instrument": "piano" }
]
}

通过异步调用,来读取json数据

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<script type="text/javascript">
var xmlHttp;
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", "Json.txt", true);
xmlHttp.send(null);
}
catch(exception)
{
alert("xmlHttp Fail");
}
}
function handleStateChange()
{
if(xmlHttp.readyState == 4)
{
if (xmlHttp.status == 200 || xmlHttp.status == 0)
{
var result = xmlHttp.responseText;
var json = eval("(" + result + ")");
alert(json.programmers[0].firstName);//读取json数据
//alert(json.sex);
}
}
}
</script>
</head>
<body>
<div>
<input type="button" value="AjaxTest" onclick="startRequest();" />
</div>
</body>
</html>
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