How to create a JQuery Clock / Timer

Question

I have a simple quiz application and I want display a nice timer / clock at the top of the page which shows the user how long they've been going for. (If I could somehow show them a timer for Total Quiz Time and also a second one for This Question Time that would be even cooler but I should be able to figure out how to do myself that once I've got one timer working.

My question is:

What's a nice, easy way to show a simple timer / clock using JQuery? (straight JS is also ok) I know how to check time, but how do I get incrementing seconds?

My own searches keep leading me to JQuery plugins (I want to roll my own) and also "event timers" which are not what I'm looking for...

Answer 1

You're looking for the setInterval function, which runs a function every x milliseconds.

For example:

var start = new Date;

setInterval(function() {
    $('.Timer').text((new Date - start) / 1000 + " Seconds");
}, 1000);

Answer 2

setInterval as suggested by SLaks was exactly what I needed to make my timer. (Thanks mate!)

Using setInterval and this great blog post I ended up creating the following function to display a timer inside my "box_header" div. I hope this helps anyone else with similar requirements!

 function get_elapsed_time_string(total_seconds) {
  function pretty_time_string(num) {
    return ( num < 10 ? "0" : "" ) + num;
  }

  var hours = Math.floor(total_seconds / 3600);
  total_seconds = total_seconds % 3600;

  var minutes = Math.floor(total_seconds / 60);
  total_seconds = total_seconds % 60;

  var seconds = Math.floor(total_seconds);

  // Pad the minutes and seconds with leading zeros, if required
  hours = pretty_time_string(hours);
  minutes = pretty_time_string(minutes);
  seconds = pretty_time_string(seconds);

  // Compose the string for display
  var currentTimeString = hours + ":" + minutes + ":" + seconds;

  return currentTimeString;
}

var elapsed_seconds = 0;
setInterval(function() {
  elapsed_seconds = elapsed_seconds + 1;
  $('#box_header').text(get_elapsed_time_string(elapsed_seconds));
}, 1000);