Simple JavaScript Timer: substring or datetime?

Question

Hi guys,

I have a label with a format ever should be: "00:00:00".

This timer should be count down via JavaScript, when the timer is 0, there should be a "Ended" in the label.

So how do it with the less performence (e.g.: I have a site with 50 timers, they need to be synchron).

My idea is to split this via substring and -1 them, check if it is -01, then decrement the number before, and set it to 59 again.

Is there an easier way?

Answer 1

I'd go with datetime, and decrement the amount of seconds. Then minutes, hours, days, months, years will be fixed, automatically. Then just have a general formatDate-function that receives a datetime and outputs your "xx:xx:xx" or "ended" depending on it.

Create a new datetime object based on todays date:

var dt = new Date();

Set it to a specific value (note that month is an enum, and starts with 0):

var dt = new Date(2009, 10, 16, 11, 50, 30); // yyyy, mm, dd, hh, mm, ss

Decrease by one second:

dt.setSeconds(dt.getSeconds()-1);

Your converters:

function dateToString(dt) {
   var h = dt.getHours();
   var m = dt.getMinutes();
   var s = dt.getSeconds();

   // ensure there are always at least two characters
   h = ('0' + h).substring(h.toString().length - 2);
   m = ('0' + m).substring(m.toString().length - 2);
   s = ('0' + s).substring(s.toString().length - 2);

   return h + ':' + m + ':' + s;
}

function stringToDate(s) {
   var dateParts = s.split(':');
   var h = parseInt(dateParts[0], 10);
   var m = parseInt(dateParts[1], 10);
   var s = parseInt(dateParts[2], 10);

   return new Date(2009, 0, 1, h, m, s); // if you're only using time, the date doesn't matter
}