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HTMLElement: transitionrun event

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The transitionrun event is fired when a CSS transition is first created, i.e. before any transition-delay has begun.

Bubbles Yes
Cancelable No
Interface TransitionEvent
Event handler property ontransitionrun

Examples

This code adds a listener to the transitionrun event:

el.addEventListener('transitionrun', () => {
  console.log('Transition is running but hasn\'t necessarily started transitioning yet');
});

The same, but using the ontransitionrun property instead of addEventListener():

el.ontransitionrun = () => {
  console.log('Transition started running, and will start transitioning when the transition delay has expired');
};

Live example

In the following example, we have a simple <div> element, styled with a transition that includes a delay:

<div class="transition">Hover over me</div>
<div class="message"></div>
.transition {
  width: 100px;
  height: 100px;
  background: rgba(255,0,0,1);
  transition-property: transform, background;
  transition-duration: 2s;
  transition-delay: 1s;
}

.transition:hover {
  transform: rotate(90deg);
  background: rgba(255,0,0,0);
}

To this, we'll add some JavaScript to indicate where the transitionstart and transitionrun events fire.

const el = document.querySelector('.transition');
const message = document.querySelector('.message');

el.addEventListener('transitionrun', function() {
  message.textContent = 'transitionrun fired';
});

el.addEventListener('transitionstart', function() {
  message.textContent = 'transitionstart fired';
});

el.addEventListener('transitionend', function() {
  message.textContent = 'transitionend fired';
});

The difference is that:

  • transitionrun fires when the transition is created (i.e. at the start of any delay).
  • transitionstart fires when the actual animation has begun (i.e. at the end of any delay).

The transitionrun will occur even if the transition is canceled before the delay expires. If there is no transition delay or if transition-delay is negative, both transitionrun and transitionstart are fired.

Specifications

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
transitionrun_event
74
79
53
No
62
13.1
74
74
53
53
13.4
11.0

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/transitionrun_event