在此页

• 特性
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

ConstrainDouble type is used to specify a constraint for a property whose value is a double-precision floating-point number. It extends the DoubleRange dictionary (which provides the ability to specify a permitted range of property values) to also support an exact value and/or an ideal value the property should take on. Additionally, you can specify the property's value as a simple floating-point value, in which case the user agent does its best to match the value once all other more stringent constraints are met.

特性

If the value of a ConstrainDouble is an object rather than a number, it may have the properties below in addition the properties it inherits from DoubleRange .

exact

A double-precision floating-point number specifying a specific, required, value the property must have to be considered acceptable.

ideal

A double-precision floating-point number specifying a value the property would ideally have, but which can be considered optional if necessary to find a match.

规范

规范	状态	注释
媒体捕获和流 The definition of 'ConstrainDouble' in that specification.	候选推荐	初始定义

Technically, ConstrainDouble is actually based on an intermediary dictionary named ConstrainDoubleRange , which adds exact and ideal to DoubleRange ，采用 ConstrainDouble being a type that can be either a long integer or a DoubleRange . However, for the sake of documentation clarity, the intermediate type (present only because of quirks in WebIDL syntax) is ignored here.

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
ConstrainDouble	Chrome Yes	Edge ≤79	Firefox 50	IE No	Opera Yes	Safari ?	WebView Android Yes	Chrome Android Yes	Firefox Android 50	Opera Android Yes	Safari iOS ?	Samsung Internet Android Yes

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
• DoubleRange
• MediaTrackConstraints
• MediaTrackCapabilities
• MediaTrackSupportedConstraints

元数据

• 最后修改： 2020 年 1 月 22 日

相关话题

1. Media Streams API
2. ConstrainDouble
3. Related pages for Media Capture and Streams

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