Animation.persist()

The persist() method of the Web Animations API's Animation interface explicitly persists an animation, when it would otherwise be removed due to the browser's Automatically removing filling animations behavior.

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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 for other methods and properties you can use to control web page animation.