Ajax基础教程（4）- 实现基本Ajax技术 4.4 创建自动刷新页面
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本文详细介绍Ajax基础教程（4）- 实现基本Ajax技术 4.4 创建自动刷新页面
代码清单4-7 dynamicUpdate.html
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Ajax Dynamic Update</title>
<script type="text/javascript">
var xmlHttp;
function createXMLHttpRequest() {
if (window.ActiveXObject) {
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
}
else if (window.XMLHttpRequest) {
xmlHttp = new XMLHttpRequest();
}
}
function doStart() {
createXMLHttpRequest();
var url = "DynamicUpdateServlet?task=reset";
xmlHttp.open("GET", url, true);
xmlHttp.onreadystatechange = startCallback;
xmlHttp.send(null);
}
function startCallback() {
if (xmlHttp.readyState == 4) {
if (xmlHttp.status == 200) {
setTimeout("pollServer()", 5000);
refreshTime();
}
}
}
function pollServer() {
createXMLHttpRequest();
var url = "DynamicUpdateServlet?task=foo";
xmlHttp.open("GET", url, true);
xmlHttp.onreadystatechange = pollCallback;
xmlHttp.send(null);
}
function refreshTime(){
var time_span = document.getElementById("time");
var time_val = time_span.innerHTML;
var int_val = parseInt(time_val);
var new_int_val = int_val - 1;
if (new_int_val > -1) {
setTimeout("refreshTime()", 1000);
time_span.innerHTML = new_int_val;
} else {
time_span.innerHTML = 5;
}
}
function pollCallback() {
if (xmlHttp.readyState == 4) {
if (xmlHttp.status == 200) {
var message =
xmlHttp.responseXML
.getElementsByTagName("message")[0].firstChild.data;
if (message != "done") {
var new_row = createRow(message);
var table = document.getElementById("dynamicUpdateArea");
var table_body =
table.getElementsByTagName("tbody").item(0);
var first_row =
table_body.getElementsByTagName("tr").item(1);
table_body.insertBefore(new_row, first_row);
setTimeout("pollServer()", 5000);
refreshTime();
}
}
}
}
function createRow(message) {
var row = document.createElement("tr");
var cell = document.createElement("td");
var cell_data = document.createTextNode(message);
cell.appendChild(cell_data);
row.appendChild(cell);
return row;
}
</script>
</head>
<body>
<h1>Ajax Dynamic Update Example</h1>
This page will automatically update itself:
<input type="button" value="Launch" id="go" onclick="doStart();"/>
<p>
Page will refresh in <span id="time">5</span> seconds.
<p>
<table id="dynamicUpdateArea" align="left">
<tbody>
<tr id="row0"><td></td></tr>
</tbody>
</table>
</body>
</html>
来源：CSDN 责编：豆豆技术应用
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