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• 句法
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

MediaTrackConstraints dictionary's facingMode 特性为 ConstrainDOMString describing the requested or mandatory constraints placed upon the value of the facingMode constrainable property.

If needed, you can determine whether or not this constraint is supported by checking the value of MediaTrackSupportedConstraints.facingMode as returned by a call to MediaDevices.getSupportedConstraints() . However, typically this is unnecessary since browsers will simply ignore any constraints they're unfamiliar with.

因为 RTP doesn't include this information, tracks associated with a WebRTC RTCPeerConnection will never include this property.

句法

var constraintsObject = { facingMode: constraint };
constraintsObject.facingMode = constraint;
					

值

An object based on ConstrainDOMString specifying one or more acceptable, ideal, and/or exact (mandatory) facing modes are acceptable for a video track.

An exact value in this case indicates that the specified facing mode is specifically required; for example:

var constraints = {
  facingMode: { exact: "user" }
};
					

This indicates that only a user-facing camera is acceptable; if there is no user-facing camera, or the user declines permission to use that camera, the media request will fail.

The following strings are permitted values for the facing mode. These may represent separate cameras, or they may represent directions in which an adjustable camera can be pointed.

"user"

The video source is facing toward the user; this includes, for example, the front-facing camera on a smartphone.

"environment"

The video source is facing away from the user, thereby viewing their environment. This is the back camera on a smartphone.

"left"

The video source is facing toward the user but to their left, such as a camera aimed toward the user but over their left shoulder.

"right"

The video source is facing toward the user but to their right, such as a camera aimed toward the user but over their right shoulder.

范例

见 Example: Constraint exerciser in Capabilities, constraints, and settings 范例。

规范

规范	状态	注释
媒体捕获和流 The definition of 'facingMode' in that specification.	候选推荐	最初的规范。

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	桌面						移动
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
facingMode	Chrome 59	Edge ≤79	Firefox 50	IE No	Opera Yes	Safari ?	WebView Android 59	Chrome Android 59	Firefox Android 50	Opera Android ?	Safari iOS ?	Samsung Internet Android 7.0

图例

完整支持

完整支持

不支持

不支持

兼容性未知 ?

兼容性未知

另请参阅

• Media Capture and Streams API
• Capabilities, constraints, and settings
• MediaTrackConstraints
• MediaDevices.getSupportedConstraints()
• MediaTrackSupportedConstraints
• MediaStreamTrack

元数据

• 最后修改： 2020 年 1 月 22 日

相关话题

1. Media Streams API
2. MediaTrackConstraints
3. 特性

   1. aspectRatio
   2. autoGainControl
   3. channelCount
   4. cursor
   5. deviceId
   6. displaySurface
   7. echoCancellation
   8. facingMode
   9. frameRate
   10. groupId
   11. height
   12. latency
   13. logicalSurface
   14. noiseSuppression
   15. sampleRate
   16. sampleSize
   17. volume
   18. width
4. Related pages for Media Capture and Streams

   1. AudioStreamTrack
   2. BlobEvent
   3. CanvasCaptureMediaStream
   4. ConstrainBoolean
   5. ConstrainDOMString
   6. ConstrainDouble
   7. ConstrainLong
   8. DoubleRange
   9. HTMLCanvasElement.captureStream()
   10. LongRange
   11. MediaDevices
   12. MediaStream
   13. MediaStreamTrack
   14. MediaStreamTrackEvent
   15. MediaTrackCapabilities
   16. MediaTrackSettings
   17. MediaTrackSupportedConstraints
   18. Navigator.mediaDevices
   19. NavigatorUserMedia
   20. NavigatorUserMediaError
   21. VideoStreamTrack
   22. navigator.mediaDevices.getUserMedia()