js 计算，显示运行时间

<script language="javascript">
//usage
/*
//start
RunTime("s");
//your code
//end
RunTime("f");

*/
var start_time;
var finish_time;
function RunTime(flag,show_id){
if (flag == "start" || flag == "s"){
start_time = new Date();
}else if (flag == "finish" || flag == "f" || flag == "end"){
finish_time = new Date();
var mms = finish_time.getTime() - start_time.getTime();
var ms = mms/1000;
var m = parseInt(ms/60);
var s = parseInt(ms%60);
var show = mms + " ms" + "<br>" + ms + " seconds <br>" + m + " minutes " + s + " seconds";
var show_alert = mms + " ms /n" + ms + " seconds /n" + m + " minutes " + s + " seconds";
if (typeof show_id != "undefined")
document.getElementById(show_id).innerHTML = show;
else alert(show_alert);
}
}
</script>