d3.timer()

d3.timer(callback[, delay[, time]])

Schedules a new timer, invoking the specified callback repeatedly until the timer is stopped. An optional numeric delay in milliseconds may be specified to invoke the given callback after a delay; if delay is not specified, it defaults to zero. The delay is relative to the specified time in milliseconds; if time is not specified, it defaults to now.

The callback is passed the (apparent) elapsed time since the timer became active. For example:

var t = d3.timer(function(elapsed) {
  console.log(elapsed);
  if (elapsed > 200) t.stop();
}, 150);

This produces roughly the following console output:

3
25
48
65
85
106
125
146
167
189
209

(The exact values may vary depending on your JavaScript runtime and what else your computer is doing.) Note that the first elapsed time is 3ms: this is the elapsed time since the timer started, not since the timer was scheduled. Here the timer started 150ms after it was scheduled due to the specified delay. The apparent elapsed time may be less than the true elapsed time if the page is backgrounded and requestAnimationFrame is paused; in the background, apparent time is frozen.

If timer is called within the callback of another timer, the new timer callback (if eligible as determined by the specified delay and time) will be invoked immediately at the end of the current frame, rather than waiting until the next frame. Within a frame, timer callbacks are guaranteed to be invoked in the order they were scheduled, regardless of their start time.