HTML animationiteration DOM Event: Reference and Examples

When someone interacts with a webpage, the browser sends events to the relevant JavaScript code. The animationiteration event happens when a repeating CSS animation completes one cycle.

When animationiteration happens

A repeating CSS animation completes one cycle.

You can listen for it using addEventListener(). That keeps event handling separate from HTML attributes such as onclick and works well with modern code organization.

A small working example

<style>
    @keyframes demoPulse { from { opacity: 1; } to { opacity: .4; } }
    .animated-box { animation: demoPulse 2s 2 alternate; }
</style>
<div id="demo-target" class="animated-box">Animate this box with CSS</div>
<p id="event-status" role="status">Waiting for animationiteration...</p>
<script>
    const eventTarget = document.getElementById("demo-target");
    const eventStatus = document.getElementById("event-status");

    if (eventTarget) {
        eventTarget.addEventListener("animationiteration", (eventDetails) => {
            eventStatus.textContent = "animationiteration event received";
            console.log(eventDetails.type, eventDetails.target);
        });
    }
</script>

Reading the code

The browser listens for animationiteration on the relevant target. When the event occurs, the callback receives eventDetails, updates the status message and logs the event name and target in Developer Tools.

Configure animation-iteration-count above one and watch successive cycles.

The CSS rule above makes the animation or transition possible. Without a real animated property, a listener alone cannot make these events fire.

Try it in your browser

Open the page, show the Console panel, and follow this test: Configure animation-iteration-count above one and watch successive cycles. Then change one thing in the example and observe whether the event still fires.

Common Beginner Mistakes

• Expecting animationiteration to fire without its required user action or browser condition.
• Configure animation-iteration-count above one and watch successive cycles.
• Adding repeated event listeners without considering cleanup or unwanted side effects.

Key Takeaways

• animationiteration reports a repeating CSS animation completes one cycle.
• addEventListener("animationiteration", ...) listens for the event on the appropriate target.
• Configure animation-iteration-count above one and watch successive cycles.