The read-only Animation.ready property of the Web Animations API returns a Promise which resolves when the animation is ready to play. A new promise is created every time the animation enters the "pending" play state as well as when the animation is canceled, since in both of those scenarios, the animation is ready to be started again.

A Promise which resolves when the animation is ready to be played. You'll typically use a construct similar to this when using the ready promise:

animation.ready.then(() => {
  // Do whatever needs to be done when
  // the animation is ready to run
});

In the following example, the state of the animation will be running when the current ready Promise is resolved because the animation does not leave the pending play state in between the calls to pause and play and hence the current ready Promise does not change.

animation.pause();
animation.ready.then(() => {
  // Displays 'running'
  alert(animation.playState);
});
animation.play();

• Web Animations API
• Animation
• Animation.playState