Animation.replaceState

The read-only Animation.replaceState property of the Web Animations API returns the replace state of the animation. This will be active if the animation has been removed, or persisted if Animation.persist() has been invoked on it.

A string that represents the replace state of the animation. The value can be one of:

• active: The initial value of the animation's replace state; when the animation has been removed by the browser's Automatically removing filling animations behavior.
• persisted: The animation has been explicitly persisted by invoking Animation.persist() on it.
• removed: The animation has been explicitly removed.

In our simple replace indefinite animations demo, you can see the following code:

const divElem = document.querySelector('div');

document.body.addEventListener('mousemove', evt => {
  let anim = divElem.animate(
    { transform: `translate(${ evt.clientX}px, ${evt.clientY}px)` },
    { duration: 500, fill: 'forwards' }
  );

  anim.commitStyles();

  //anim.persist()

  anim.onremove = event => {console.log('Animation removed');}

  console.log(anim.replaceState);
});

Here we have a <div> element, and an event listener that fires the event handler code whenever the mouse moves. The event handler sets up an animation that animates the <div> element to the position of the mouse pointer. This could result in a huge animations list, which could create a memory leak. For this reason, modern browsers automatically remove overriding forward filling animations.

You can see the replaceState of the animation being logged at the end of the handler. This will be active for each animation by default, or persisted if the persist() call is uncommented.

• Web Animations API
• Animation