Animation: remove event

The remove event of the Animation interface fires when the animation is automatically removed by the browser.

Syntax

Use the event name in methods like addEventListener(), or set an event handler property.

js
addEventListener("remove", (event) => { })

onremove = (event) => { }

Event type

An AnimationPlaybackEvent. Inherits from Event.

EventAnimationPlaybackEvent

Examples

undefined

Removing replaced animations

In this example we have a <button id="start"> element, and an event listener that runs whenever the mouse moves. The mousemove event handler sets up an animation that animates the <button> 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 forwards-filling animations that are overridden by other animations.

The number of animations created is displayed. A remove event listener is used to count and display the number of animations removed as well.

All but one of the animations should eventually be removed.

HTML

html
<button id="start">Click to drag</button>
<br />
<button id="reset">Reset example</button>
<p>
  Click the button to start the animation (disabled by default to protect those
  who suffer migraines when experiencing such animations).
</p>
<p>Animations created: <span id="count-created">0</span></p>
<p>Animations removed: <span id="count-removed">0</span></p>

CSS

css
:root,
body {
  margin: 0;
  padding: 0;
  height: 100%;
}

button {
  margin: 0.5rem 0;
}

JavaScript

js
const button = document.querySelector("#start");
let created = 0;
let removed = 0;

button.addEventListener(
  "click",
  () => {
    document.body.addEventListener("mousemove", (event) => {
      const animation = button.animate(
        { transform: `translate(${event.clientX}px, ${event.clientY}px)` },
        { duration: 500, fill: "forwards" },
      );
      created++;
      showCounts();

      // the remove event fires after the animation is removed
      animation.addEventListener("remove", () => {
        removed++;
        showCounts();
      });
    });
  },
  { once: true },
);

function showCounts() {
  document.getElementById("count-created").textContent = created;
  document.getElementById("count-removed").textContent = removed;
}

const reset = document.querySelector("#reset");
reset.addEventListener("click", () => {
  document.location.reload();
});

Result

Specifications

See also