.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
var currentTime = Animation.currentTime; Animation.currentTime = newTime;
A number representing the current time in milliseconds, or
null to deactivate the animation.
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
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.
The definition of 'currentTime' in that specification.