d3-timer

What is d3-timer?

The d3-timer package provides a set of tools for controlling the timing of animations, transitions, and other time-based operations. It allows for the efficient scheduling of new timers, the creation of timer queues, and the handling of elapsed time within scheduled callbacks.

What are d3-timer's main functionalities?

Creating and starting a timer

This feature allows you to create a new timer that calls a specified callback function on each animation frame with the elapsed time. The timer can be stopped by calling the stop method.

const timer = d3.timer(elapsed => {
  console.log('Timer elapsed time:', elapsed);
  if (elapsed > 2000) timer.stop();
});

Creating a timer with a delay and time limit

This feature allows you to create a timer with a delay before it starts invoking the callback function. The timer will automatically stop after a specified time limit.

const timer = d3.timer(elapsed => {
  console.log('Timer elapsed time with delay:', elapsed);
  if (elapsed > 1000) timer.stop();
}, 500);

Creating a timer queue

This feature allows you to create a queue of timers that will execute their callback functions after a specified delay. It is similar to using setTimeout but is integrated with the d3-timer's efficient timing mechanism.

const timer1 = d3.timeout(() => console.log('Timeout 1'), 1000);
const timer2 = d3.timeout(() => console.log('Timeout 2'), 2000);

Creating an interval timer

This feature allows you to create a timer that will execute its callback function at a specified interval. It is similar to using setInterval but provides more accurate and efficient timing.

const interval = d3.interval(() => {
  console.log('Interval tick');
  if (++count > 10) interval.stop();
}, 1000);

Other packages similar to d3-timer

raf-schd

raf-schd provides a scheduler for requestAnimationFrame, allowing you to throttle rendering updates for better performance. It is similar to d3-timer in that it helps manage animations, but it focuses on scheduling within the animation frame rate.

chrono-node

chrono-node is a high-resolution timer utility for Node.js, which can be used for performance testing and benchmarking. It offers precise timing but does not provide the same scheduling features as d3-timer.

later

later is a library for describing recurring schedules and calculating their occurrences. It provides a different set of features compared to d3-timer, focusing on recurring schedules rather than frame-based animation timing.

README

d3-timer

This module provides an efficient queue capable of managing thousands of concurrent animations, while guaranteeing consistent, synchronized timing with concurrent or staged animations. Internally, it uses requestAnimationFrame for fluid animation (if available), switching to setTimeout for delays longer than 24ms.

Installing

If you use NPM, npm install d3-timer. Otherwise, download the latest release. The released bundle supports AMD, CommonJS, and vanilla environments. Create a custom build using Rollup or your preferred bundler. You can also load directly from d3js.org:

<script src="https://d3js.org/d3-timer.v0.2.min.js"></script>

In a vanilla environment, a d3_timer global is exported. Try d3-timer in your browser.

API Reference

# 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 since UNIX epoch; if time is not specified, it defaults to Date.now.

The callback is passed two arguments when it is invoked: the elapsed time since the timer became active, and the current time, now. The latter is useful for precise scheduling of secondary timers. For example:

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

This produced the following console output:

6 1433806724202
26 1433806724222
51 1433806724247
73 1433806724269
92 1433806724288
114 1433806724310
132 1433806724328
152 1433806724348
171 1433806724367
191 1433806724387
213 1433806724409

Note that the first elapsed is 6ms, since this is the elapsed time since the timer started (after the 150ms delay), not the elapsed time since the timer was scheduled.

Use delay and time to specify relative and absolute moments in time when the callback should start being invoked. For example, a calendar notification for four hours before midnight on October 29, 2012 might be coded as:

d3.timer(callback, -4 * 1000 * 60 * 60, new Date(2012, 09, 29));

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).

# timer.restart(callback[, delay[, time]])

Restart a timer with the specified callback and optional delay and time. This is equivalent to stopping this timer and creating a new timer with the specified arguments, although this timer retains the original invocation priority.

# timer.stop()

Stops this timer, preventing subsequent callbacks. This method has no effect if the timer has already stopped.

# d3.timerOnce(callback[, delay[, time]])

Like timer, except the timer automatically stops on its first callback.

# d3.timerFlush([time])

Immediately execute (invoke once) any eligible timer callbacks. If time is specified, it represents the current time; if not specified, it defaults to Date.now. Specifying an explicit time helps ensure deterministic behavior.

Note that zero-delay timers are normally first executed after one frame (~17ms). This can cause a brief flicker because the browser renders the page twice: once at the end of the first event loop, then again immediately on the first timer callback. By flushing the timer queue at the end of the first event loop, you can run any zero-delay timers immediately and avoid the flicker.