无刷新XMLHttp的几个问题
申明方式:
var xhImgList;
try {
xhImgList = new ActiveXObject("Microsoft.XMLHTTP");
} catch(e) {
try {
xhImgList=new ActiveXObject("MSXML2.XMLHTTP");
} catch(e) {
xhImgList=new XMLHttpRequest(); } }
解决 XMLHTTP 的缓存问题:
IE 中 XMLHTTP 默认会将内容缓存,GET 方式下只要 URL 没有变化,就会直接使用缓存,不发送任何请求。在网上查找到在Html头加上
<meta http-equiv="pragma" c>
<meta http-equiv="Cache-Control" c>
<meta http-equiv="expires" c>
经过测试以上方法没有用,后在调用 send 方法前设置 If-Modified-Since 头为一个比较早的日期。如使用
xmlhttp.setRequestHeader("If-Modified-Since", "Sat, 1 Jan 2000 00:00:00 GMT");
经测试以上方面有效!
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