Animation: persist() method

The persist() method of the Web Animations API’s Animation interface explicitly persists an animation, preventing it from being automatically removed when it is replaced by another animation.

Syntax

persist()

Parameters

None.

Return value

None (undefined).

Examples

Using persist()

In this example, we have three buttons:

• “Add persistent animation” and “Add transient animation” each add a new transform animation to the red square. The animations alternate direction: so the first is left to right, the second is right to left, and so on. “Add persistent animation” calls persist() on the animation it creates.

• The third button, “Cancel an animation”, cancels the most recently added animation.

The example displays a list of all animations that have not been canceled, in the order they were added, along with each animation’s replaceState.

HTML

<div id="animation-target"></div>
<button id="start-persistent">Add persistent animation</button>
<button id="start-transient">Add transient animation</button>
<button id="cancel">Cancel an animation</button>
<ol id="stack"></ol>

<template id="list-item-template">
  <li>
    <span class="replaceState"></span>,
    <span class="description"></span>
  </li>
</template>

CSS

div {
  width: 100px;
  height: 100px;
  background: red;
  transform: translate(100px);
}

JavaScript

const target = document.getElementById("animation-target");
const persistentButton = document.getElementById("start-persistent");
const transientButton = document.getElementById("start-transient");
const cancelButton = document.getElementById("cancel");
persistentButton.addEventListener("click", () => startAnimation(true));
transientButton.addEventListener("click", () => startAnimation(false));
cancelButton.addEventListener("click", cancelTop);
const stack = [];

let offset = -100;

function startAnimation(persist) {
  offset = -offset;
  const animation = target.animate(
    { transform: `translate(${100 + offset}px)` },
    { duration: 500, fill: "forwards" },
  );
  stack.push(animation);
  if (persist) {
    animation.persist();
  }
  // Add the animation to the displayed stack (implementation not shown)
  show(animation, offset);
}

function cancelTop() {
  stack.pop()?.cancel();
}

const stackDisplay = document.getElementById("stack");
const template =
  document.getElementById("list-item-template").content.firstElementChild;
const nodes = new Map();

function show(animation, offset) {
  const direction = offset < 0 ? "left" : "right";
  const li = template.cloneNode(true);
  const description = li.querySelector(".description");
  const replaceState = li.querySelector(".replaceState");
  description.textContent = direction;
  replaceState.textContent = animation.replaceState;
  nodes.set(animation, { li, description, replaceState });
  stackDisplay.append(li);
  animation.addEventListener("cancel", () => {
    nodes.get(animation).li.remove();
    nodes.delete(animation);
  });
  animation.addEventListener("remove", () => {
    nodes.get(animation).replaceState.textContent = animation.replaceState;
  });
}

Result

Note that adding a new transient animation will replace any previously added transient animation. Those animations will be automatically removed, and their replaceState will be "removed". However, persistent animations will not be removed.

Also note that removed animations don’t affect the display; the position of the <div> is determined by the most recent active or persisted animation.

Specifications

Browser compatibility

See also

• Web Animations API
• Animation for other methods and properties you can use to control web page animation.
• replaceState
• remove event