Bullet-timing

A small library for modifying the playback speed of CSS- and JS-animations, setTimeout and setInterval. Works with GSAP and requestAnimationFrame.

Installation

As a module
npm install bullet-timing

As a script
<script src="https://cdn.jsdelivr.net/npm/bullet-timing/bin/index.min.js"></script>

Usage

As a module

import timing, { css } from 'bullet-timing'

// Set the global playback rate to 20%
timing.setPlaybackRate(0.2)

// Set the playback rate of CSS to 10%
css.setPlaybackRate(0.1)

// ...do animations

As a script

<!-- Load the script before any other scripts -->
<script src="https://cdn.jsdelivr.net/npm/bullet-timing/bin/index.min.js"></script>

<script defer>
  // Set the global playback rate to 20%
  timing.setPlaybackRate(0.2)

  // Set the playback rate of CSS to 10%
  timing.css.setPlaybackRate(0.1)

  // ...do animations
</script>

.setPlaybackRate(rate)

Set the global playback rate.

.css.setPlaybackRate(rate)

Set the playback rate exclusively for CSS-animations. This affects both the duration and the delay of animations and transitions.

.date.setPlaybackRate(rate)

Set the playback rate exclusively for the Date object. This will cause Date.now() to return a simulated value based on the rate.

.timeout.setPlaybackRate(rate)

Set the playback rate exclusively for setTimeout and setInterval. This will result in the provided timeout being slower or faster based on the rate.

Note: Already set timeouts and intervals will not be affected.

How it works

CSS

In order to support CSS animations and transitions this library modifies any specified animation-duration, animation-delay, transition-duration or transition-delay to scale with the specified rate.

Date

In order to support GSAP and requestAnimationFrame, window.Date.now() is overridden to return a simulated timestamp as if the time has been slowed down or sped up. This may cause unexpected side effects in your application as Date.now() is often used for more than just animations. However, Date.getTime() and other date-functions are not modified.

setTimeout and setInterval

Since these two functions are often used to delay and synchronise animations, both window.setTimeout and window.setInterval are overridden to make use of the playback rate.

License

MIT