JS计时

   /*
    var obj = document.getElementById("times");

    var ms = 0;
    var state = 0;
    function startstop() {
        if (state == 0) {
            state = 1;
            then = new Date();
            then.setTime(then.getTime() - ms);
        } else {
            state = 0;
            now = new Date();
            ms = now.getTime() - then.getTime();
            obj.innerHTML = ms/1000;
        }
    } 
 
    function display() {
        setTimeout("display();", 50);
        if (state == 1) {
            now = new Date();
            ms = now.getTime() - then.getTime();
            obj.innerHTML = ms/1000;
        }
    }
   // window.onload = display
    window.onbeforeunload = function () {
        display();
        //alert('exit');
    }
    startstop();
    */