TextTrackList

TextTrackList interface is used to represent a list of the text tracks defined by the <track> element, with each track represented by a separate textTrack object in the list.

Retrieve an instance of this object with HTMLMediaElement.textTracks . The individual tracks can be accessed using array syntax or functions such as forEach() 例如。

特性

This interface also inherits properties from its parent interface, EventTarget .

length 只读
The number of tracks in the list.

事件处理程序

onaddtrack
An event handler to be called when the addtrack event is fired, indicating that a new text track has been added to the media element.
onchange
An event handler to be called when the change event occurs.
onremovetrack
An event handler to call when the removetrack event is sent, indicating that a text track has been removed from the media element.

方法

This interface also inherits methods from its parent interface, EventTarget .

getTrackById()
返回 TextTrack found within the TextTrackList whose id matches the specified string. If no match is found, null 被返回。

Events

addtrack
Fired when a new text track has been added to the media element.
Also available via the onaddtrack 特性。
change
Fired when a text track has been made active or inactive.
Also available via the onchange 特性。
removetrack
Fired when a new text track has been removed from the media element.
Also available via the onremovetrack 特性。

Usage notes

In addition to being able to obtain direct access to the text tracks present on a media element, TextTrackList lets you set event handlers on the addtrack and removetrack events, so that you can detect when tracks are added to or removed from the media element's stream. See onaddtrack and onremovetrack for details and examples.

范例

Getting a video element's text track list

To get a media element's TextTrackList , use its textTracks 特性。

var textTracks = document.querySelector("video").textTracks;
					

Monitoring track count changes

In this example, we have an app that displays information about the number of channels available. To keep it up to date, handlers for the addtrack and removetrack events are set up.

textTracks.onaddtrack = updateTrackCount;
textTracks.onremovetrack = updateTrackCount;
function updateTrackCount(event) {
  trackCount = textTracks.length;
  drawTrackCountIndicator(trackCount);
}
					

规范

规范 状态 Comment
HTML Living Standard
The definition of 'TexTrackList' in that specification.
实时标准

浏览器兼容性

更新 GitHub 上的兼容性数据
Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
TextTrackList Chrome Yes Edge ≤18 Firefox Yes IE ? Opera Yes Safari Yes WebView Android Yes Chrome Android Yes Firefox Android ? Opera Android Yes Safari iOS ? Samsung Internet Android Yes
addTrack event Chrome Yes Edge ≤79 Firefox ? IE ? Opera ? Safari ? WebView Android Yes Chrome Android Yes Firefox Android ? Opera Android ? Safari iOS ? Samsung Internet Android Yes
change event Chrome Yes Edge ≤79 Firefox ? IE ? Opera ? Safari ? WebView Android Yes Chrome Android Yes Firefox Android ? Opera Android ? Safari iOS ? Samsung Internet Android Yes
getTrackById Chrome Yes Edge 18 Firefox Yes IE ? Opera ? Safari 6 WebView Android Yes Chrome Android Yes Firefox Android ? Opera Android ? Safari iOS ? Samsung Internet Android Yes
length Chrome 44 Edge ≤18 Firefox Yes IE ? Opera 31 Safari 10 WebView Android 44 Chrome Android 44 Firefox Android ? Opera Android 32 Safari iOS ? Samsung Internet Android 4.0
removeTrack event Chrome Yes Edge ≤79 Firefox ? IE ? Opera ? Safari ? WebView Android Yes Chrome Android Yes Firefox Android ? Opera Android ? Safari iOS ? Samsung Internet Android Yes

图例

完整支持
完整支持
兼容性未知
兼容性未知
  1. TextTrackList
  2. 特性
    1. length
    2. onaddtrack
    3. onchange
    4. onremovetrack
  3. 方法
    1. getTrackById()
  4. Events
    1. change
  5. 继承:
    1. EventTarget
  6. Related pages for HTML DOM
    1. BeforeUnloadEvent
    2. DOMStringMap
    3. ErrorEvent
    4. GlobalEventHandlers
    5. HTMLAnchorElement
    6. HTMLAreaElement
    7. HTMLAudioElement
    8. HTMLBRElement
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    10. HTMLBaseFontElement
    11. HTMLBodyElement
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    14. HTMLContentElement
    15. HTMLDListElement
    16. HTMLDataElement
    17. HTMLDataListElement
    18. HTMLDialogElement
    19. HTMLDivElement
    20. HTMLDocument
    21. HTMLElement
    22. HTMLEmbedElement
    23. HTMLFieldSetElement
    24. HTMLFormControlsCollection
    25. HTMLFormElement
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    27. HTMLHRElement
    28. HTMLHeadElement
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    40. HTMLMapElement
    41. HTMLMediaElement
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    70. HTMLTableSectionElement
    71. HTMLTemplateElement
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    73. HTMLTimeElement
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    75. HTMLTrackElement
    76. HTMLUListElement
    77. HTMLUnknownElement
    78. HTMLVideoElement
    79. HashChangeEvent
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