var xmlHttp;
var timer = null;
var timerRunning = false;
var url;

    function createXMLHttpRequest() {
        if(window.XMLHttpRequest) {
            xmlHttp = new XMLHttpRequest();
        } else if (window.ActiveXObject) {
            xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
        }
    }

    function statusStop (){
        if(timerRunning){
              clearTimeout(timer);
        }
        timerRunning = true;
    }

    /* ------------------- 间隔查询 ------------------- */
    function autoDeep(){
        createXMLHttpRequest();
        url = "map.php?refresh="+Math.random();
        method = "GET";
        xmlHttp.open(method,url,true);
        xmlHttp.onreadystatechange = null;
        xmlHttp.send(null);
        timerRunning = false;
        timer = setTimeout('autoDeep()',5000);  //5秒执行一次
    }

    function statusBegin(){
        statusStop();
        autoDeep();
    }

    statusBegin();