Timer control

<!DOCTYPE html>
<html>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">

<body>

<button class="play">Play</button>
<button class="pause">Pause</button>
<button class="reset">Reset</button>

</body>

var time = d3.select('body').append('h1');
var timeTimer = new TimerControl(function(t) { time.text(t); });

d3.select('.play').on('click', timeTimer.play);
d3.select('.pause').on('click', timeTimer.pause);
d3.select('.reset').on('click', timeTimer.reset);

// `fn` will be called with context `context` if supplied (optional)
function TimerControl(fn, context) {

var epoch = 0;
  var running = false;

// initialize, effectively
  fn.call(context || this, epoch);

this.play = function() {
    if(running) return;
    running = true;
    d3.timer(function(t) {
      fn.call(context || this, epoch + t);
      if (!running) {
        epoch += t;
        return true;
      }
      return false;
    })
  }

this.pause = function() {
    running = false;
  }

this.reset = function() {
    epoch = 0;
    fn.call(context || this, epoch);
  }

}
  
</script>
</html>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.6/d3.min.js