Repeating setTimeout

Question

I am trying to repeat setTimeout every 10 seconds. I know that setTimeout by default only waits and then performs an action one time. How can I rep

Answer 1

Here is a function using setTimeout that tried to call itself as close as it can to a regular interval. If you watch the output, you can see the time drifting and being reset.

<script type="text/javascript">

function Timer(fn, interval) {
  this.fn = fn;
  this.interval = interval;
}

Timer.prototype.run = function() {

    var timer = this;
    var timeDiff = this.interval;
    var now = new Date();  // Date.now is not supported by IE 8
    var newInterval;

    // Only run if all is good
    if (typeof timer.interval != 'undefined' && timer.fn) {

      // Don't do this on the first run
      if (timer.lastTime) {
        timeDiff = now - timer.lastTime;
      }
      timer.lastTime = now;

      // Adjust the interval
      newInterval = 2 * timer.interval - timeDiff;

      // Do it
      timer.fn();

      // Call function again, setting its this correctly
      timer.timeout = setTimeout(function(){timer.run()}, newInterval);
  }
}


var t = new Timer(function() {
  var d = new Date();
  document.getElementById('msg').innerHTML = d + ' : ' + d.getMilliseconds();
}, 1000);


window.onload = function() {
  t.run();
};
</script>

<span id="msg"></span>