jquery ajax监听事件

var oldComparePeriod = "";
var newComparePeriod = "";
$(function(){

//将新的期数值放进去
newComparePeriod = $('#comparePeriod').combobox('getValue');
//启动监听器
setInterval("ajaxListener()",5000);//每5秒监听一次

});
// 监听器
function ajaxListener(){
newComparePeriod = $('#comparePeriod').combobox('getValue');
//期数change时向后台发送请求
if(newComparePeriod == oldComparePeriod)
return ;
oldComparePeriod = newComparePeriod;
var data = {comparePeriod:oldComparePeriod};
jQuery.ajax({ //发送请求
type: 'post',
url : 'selectComparePeriod.htm',
dataType:'json',
data: data,
success: function(rs){
if(rs==null || rs.length==0){
return ;
}else{
var period = rs[0];
var beginNearDate = period.beginNearDate;
var beginDate = period.beginDate;
var endDate = period.endDate;
document.getElementById('beginNearDate').innerText=beginNearDate;
document.getElementById('beginDate').innerText=beginDate;
document.getElementById('endDate1').innerText=endDate;
document.getElementById('endDate2').innerText=endDate;
/*
$('#beginNearDate').textbox('setValue',beginNearDate);
$('#beginDate').textbox('setValue',beginDate);
$('#endDate1').textbox('setValue',endDate);
$('#endDate2').textbox('setValue',endDate);
*/
}
},
error:function(){
jQuery.messager.alert('提示', '服务器正忙，请稍后重试。');//异常提示
}
});
}