//为url添加时间戳
//time 为多长时间改变一次时间戳,以小时为单位
function setTimeStamp(url, time){
var time = time || 4,
timeStamp = "timeStamp=" + Math.floor(new Date()/(time * 36e5));
return url.indexOf("?") < 0 ? (url + "?" + timeStamp) : (url + "&" + timeStamp);
}