如何避免用户添加断点来停止js中的倒数计时器？

Question

I've been working on a online test system.User takes test in a limited time. So I use js timer function.

 function timer(intDiff){
    window.setInterval(function(){

    var minute=0,
        second=0;       
    if(intDiff > 0){

        minute = Math.floor(intDiff / 60);
        second = Math.floor(intDiff) - (minute * 60);
    }
    if (minute <= 9) minute = '0' + minute;
    if (second <= 9) second = '0' + second;

    $('#minute_show').html('<s></s>'+minute+'minute');
    $('#second_show').html('<s></s>'+second+'second');
    intDiff--;
    }, 1000);
} 

$(function(){
    timer(intDiff);
}); 

but user can add breakpoint in chrome to make the time stop. How do I avoid user to do that.I know I can check the server time and client submit time.Is there any easy and better solution?

Answer 1

Short answer, you can't.

Long answer:

You're design is bad, you should base your time measurement using the date object. Each time a loop will get triggered, check the current date with new Date() and keep track of the last date.

Keep in mind that even if you set an interval of 1000ms, it doesn't mean that on the function will get called every seconds. It only means that it will never get called before 1000ms. As Javascript runs in one thread, any blocking process may delay calling methods that will remain in the event queue ( setInterval in this case).

This way, it might not be necessary to track server time this way.