HTMLElement: transitionrun event

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

Specification Status Comment
CSS Transitions Level 2
The definition of 'transitionstart' in that specification.
Editor's Draft Initial definition.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
transitionrun eventChrome Full support 74Edge ? Firefox Full support 53IE ? Opera ? Safari ? WebView Android Full support 74Chrome Android Full support 74Edge Mobile ? Firefox Android Full support 53Opera Android ? Safari iOS ? Samsung Internet Android ?

Legend

Full support  
Full support
Compatibility unknown  
Compatibility unknown

See also

Document Tags and Contributors

Last updated by: Konrud,