EffectTiming.direction - Web APIs 编辑

Experimental

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

The direction property of the Web Animations API dictionary EffectTiming indicates an animation's playback direction along its timeline, as well as its behavior when it reaches the end of an iteration

Element.animate(), KeyframeEffectReadOnly(), and KeyframeEffect() all accept an object of timing properties including direction. The value of direction corresponds directly to AnimationEffectTimingReadOnly.direction in timing objects returned by AnimationEffectReadOnly, KeyframeEffectReadOnly, and KeyframeEffect.

Syntax

var timingProperties = {
  direction: "normal" | "reverse" | "alternate" | "alternate-reverse"
};

timingProperties.direction = "normal" | "reverse" | "alternate" | "alternate-reverse";

Value

A DOMString which specifies the direction in which the animation should play as well as what to do when the playback reaches the end of the animation sequence in the current direction. It can take one of the following values, with the default being "normal":

"normal"

The animation runs forwards, from beginning to end, in the way we experience the flow of time.

"reverse"

The animation runs backwards, or "rewinds."

"alternate"

The animation switches direction after each iteration, going forward through the animation sequence the first iteration, then backward through the sequence the second iteration, and so forth.

"alternate-reverse"

Similar to "alternate", except the animation playback starts by going from the end of the animation sequence toward the beginning the first iteration, then goes forward during the second, and so forth.

Examples

In the Forgotten Key example, Alice waves her arm up and down by passing her an alternate value for her direction property:

// Get Alice's arm, and wave it up and down
document.getElementById("alice_arm").animate([
  { transform: 'rotate(10deg)' },
  { transform: 'rotate(-40deg)' }
], {
  easing: 'steps(2, end)',
  iterations: Infinity,
  direction: 'alternate',
  duration: 600
});

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Web Animations API
• Element.animate(), KeyframeEffectReadOnly(), and KeyframeEffect() all accept an object of timing properties including this one.
• The value of this property corresponds to the one in AnimationEffectTimingReadOnly (which is the timing object for AnimationEffectReadOnly, KeyframeEffectReadOnly, and KeyframeEffect).
• CSS's animation-direction