MediaTrackSupportedConstraints.deviceId - Web APIs 编辑

The MediaTrackSupportedConstraints dictionary's deviceId property is a read-only Boolean value which is present (and set to true) in the object returned by MediaDevices.getSupportedConstraints() if and only if the user agent supports the deviceId constraint. If the constraint isn't supported, it's not included in the list, so this value will never be false.

You can access the supported constraints dictionary by calling navigator.mediaDevices.getSupportedConstraints().

Syntax

deviceIdConstraintSupported = supportedConstraintsDictionary.deviceId;

Value

This property is present in the dictionary (and its value is always true) if the user agent supports the deviceId constraint. If the property isn't present, this property is missing from the supported constraints dictionary, and you'll get undefined if you try to look at its value.

Example

HTML content

<div id="result">
</div>

CSS content

#result {
  font: 14px "Arial", sans-serif;
}

JavaScript content

let result = document.getElementById("result");

if (navigator.mediaDevices.getSupportedConstraints().deviceId) {
  result.textContent = "Supported!";
} else {
  result.textContent = "Not supported!";
}

Result

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Media Capture and Streams API
• MediaDevices.getSupportedConstraints()
• MediaTrackSupportedConstraints
• MediaStreamTrack