/**
 * 简单AJAX封装
 * 如果使用sendRequest(url,srcObj)方法,srcObj 为null时需要在调用页覆盖processRequest()方法
 * 覆盖其他方法时，注意书写顺序，JS只认同方法名最后一个实现，而不管参数是否相同
 */
var request = false;
try{
	request = new XMLHttpRequest();
}catch (trymicrosoft) {
	try{
		request = new ActiveXObject("Msxml2.XMLHTTP");
	}catch (othermicrosoft) {
		try{
			request = new ActiveXObject("Microsoft.XMLHTTP");
		}catch (failed) {
			request = false;
		}
	}
}

if (!request){
  alert("");
}
function sendRequest(url,srcObj,timeout){
	request.open("POST", url, true);
	if(srcObj == null){
		request.onreadystatechange = processRequest;
	}else{
		request.onreadystatechange = function(){
			if (request.readyState == 4) {
				if (request.status == 200) {
					srcObj.value = request.responseText;
			   	}else if (request.status == 404){
					alert("");
				}else{
					alert("" + request.status);
				}
			}
		};
	}
	request.send(null);
	if(timeout != -1){
		timeoutid = setTimeout("sendRequest('"+url+"',null,"+timeout+")",timeout)
	}
}
/**
 * 需要自己覆盖实现
 */
function processRequest(){}