The TransitionEvent.elapsedTime read-only property is a float giving the amount of time the animation has been running, in seconds, when this event fired. This value is not affected by the transition-delay property. 
 The TransitionEvent.elapsedTime read-only property is a float giving the amount of time the animation has been running, in seconds, when this event fired. This value is not affected by the transition-delay property. 
A number.
| Specification | 
|---|
| CSS Transitions  # Events-TransitionEvent-elapsedTime  | 
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | |
elapsedTime | 
2 | 12 | 4 | 10 | ≤12.1 | 6 | 4.4 | 18 | 4 | ≤12.1 | 6 | 1.0 | 
    © 2005–2023 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
    https://developer.mozilla.org/en-US/docs/Web/API/TransitionEvent/elapsedTime