Animation.playbackRate - Web APIs 编辑

Experimental

This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The Animation.playbackRate property of the Web Animations API returns or sets the playback rate of the animation.

Animations have a playback rate that provides a scaling factor from the rate of change of the animation's timeline time values to the animation’s current time. The playback rate is initially 1.

Syntax

var currentPlaybackRate = Animation.playbackRate;

Animation.playbackRate = newRate;

Value

Takes a number that can be 0, negative, or positive. Negative values reverse the animation. The value is a scaling factor, so for example a value of 2 would double the playback rate.

Setting an animation’s playbackRate to 0 effectively pauses the animation (however, its playstate does not necessarily become paused).

Examples

In the Growing/Shrinking Alice Game example, clicking or tapping the bottle causes Alice's growing animation (aliceChange) to reverse, causing her to shrink:

var shrinkAlice = function() {
  aliceChange.playbackRate = -1;
  aliceChange.play();
}

// On tap or click, Alice will shrink.
bottle.addEventListener("mousedown", shrinkAlice, false);
bottle.addEventListener("touchstart", shrinkAlice, false);

Contrariwise, clicking on the cake causes her to "grow," playing aliceChange forwards again:

var growAlice = function() {
  aliceChange.playbackRate = 1;
  aliceChange.play();
}

// On tap or click, Alice will grow.
cake.addEventListener("mousedown", growAlice, false);
cake.addEventListener("touchstart", growAlice, false);

In another example, the Red Queen's Race Game, Alice and the Red Queen are constantly slowing down:

setInterval( function() {

  // Make sure the playback rate never falls below .4

  if (redQueen_alice.playbackRate > .4) {
    redQueen_alice.playbackRate *= .9;
  }

}, 3000);

But clicking or tapping on them causes them to speed up by multiplying their playbackRate:

var goFaster = function() {
  redQueen_alice.playbackRate *= 1.1;
}

document.addEventListener("click", goFaster);
document.addEventListener("touchstart", goFaster);

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Web Animations API
• Animation