The TextTrackList property onchange is an event handler which is called when the change event occurs, indicating that a change has occurred on a TextTrack in the VideoTrackList. 
 Note: You can also add a handler for the change event using addEventListener(). 
TextTrackList.onchange = eventHandler;
 This snippet establishes a handler for the change event that looks at each of the tracks in the list, calling a function to update the state of a user interface control that indicates the current state of the track. 
var trackList = document.querySelector("video, audio").textTracks; trackList.onchange = function(event) { .... /* do something */ };
| Specification | 
|---|
| HTML Standard (HTML) # handler-tracklist-onchange  | 
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | |
onchange | 
33  | 
18  | 
31  | 
No  | 
20  | 
7  | 
4.4  | 
33  | 
31  | 
20  | 
7  | 
2.0  | 
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    https://developer.mozilla.org/en-US/docs/Web/API/TextTrackList/onchange