Element: transitionstart event
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2015.
The transitionstart
event is fired when a CSS transition has actually started, i.e., after any transition-delay
has ended.
This event is not cancelable.
Syntax
Use the event name in methods like addEventListener()
, or set an event handler property.
addEventListener("transitionstart", (event) => {});
ontransitionstart = (event) => {};
Event type
A TransitionEvent
. Inherits from Event
.
Event properties
Also inherits properties from its parent Event
.
TransitionEvent.propertyName
Read only-
A string containing the name CSS property associated with the transition.
TransitionEvent.elapsedTime
Read only-
A
float
giving the amount of time the transition has been running, in seconds, when this event fired. This value is not affected by thetransition-delay
property. TransitionEvent.pseudoElement
Read only-
A string, starting with
::
, containing the name of the pseudo-element the animation runs on. If the transition doesn't run on a pseudo-element but on the element, an empty string:''
.
Examples
This code adds a listener to the transitionstart
event:
element.addEventListener("transitionstart", () => {
console.log("Started transitioning");
});
The same, but using the ontransitionstart
property instead of addEventListener()
:
element.ontransitionstart = () => {
console.log("Started transitioning");
};
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: rgb(255 0 0 / 100%);
transition-property: transform, background;
transition-duration: 2s;
transition-delay: 1s;
}
.transition:hover {
transform: rotate(90deg);
background: rgb(255 0 0 / 0%);
}
To this, we'll add some JavaScript to indicate where the transitionstart
and transitionrun
events fire.
const transition = document.querySelector(".transition");
const message = document.querySelector(".message");
transition.addEventListener("transitionrun", () => {
message.textContent = "transitionrun fired";
});
transition.addEventListener("transitionstart", () => {
message.textContent = "transitionstart fired";
});
transition.addEventListener("transitionend", () => {
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).
Specifications
Specification |
---|
CSS Transitions # transitionstart |
Browser compatibility
BCD tables only load in the browser
See also
- The
TransitionEvent
interface - CSS properties:
transition
,transition-delay
,transition-duration
,transition-property
,transition-timing-function
- Related events:
transitionend
,transitionrun
,transitioncancel