Animation.currentTime - Web APIs 编辑

Experimental

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

The Animation.currentTime property of the Web Animations API returns and sets the current time value of the animation in milliseconds, whether running or paused.

If the animation lacks a timeline, is inactive, or hasn't been played yet, currentTime's return value is null.

Syntax

var currentTime = Animation.currentTime;
Animation.currentTime = newTime;

Value

A number representing the current time in milliseconds, or null to deactivate the animation.

Examples

In the Drink Me/Eat Me game, Alice's height is animated so it can go from small to large or large to small. At the start of the game, her height is set between the two extremes by setting her animation's currentTime to half her KeyframeEffect's duration:

aliceChange.currentTime = aliceChange.effect.timing.duration / 2;

A more generic means of seeking to the 50% mark of an animation would be:

animation.currentTime =
  animation.effect.getComputedTiming().delay +
  animation.effect.getComputedTiming().activeDuration / 2;

Reduced time precision

To offer protection against timing attacks and fingerprinting, the precision of animation.currentTime might get rounded depending on browser settings.
In Firefox, the privacy.reduceTimerPrecision  preference is enabled by default and defaults to 20us in Firefox 59; in 60 it will be 2ms.

// reduced time precision (2ms) in Firefox 60
animation.currentTime;
// 23.404
// 24.192
// 25.514
// ...

// reduced time precision with `privacy.resistFingerprinting` enabled
animation.currentTime;
// 49.8
// 50.6
// 51.7
// ...

In Firefox, you can also enabled privacy.resistFingerprinting, the precision will be 100ms or the value of privacy.resistFingerprinting.reduceTimerPrecision.microseconds, whichever is larger.

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Animation for other methods and properties you can use to control web page animation.
• Animation.startTime for the time an animation is scheduled to start.
• Web Animations API