MediaDeviceInfo.groupId - Web APIs 编辑

The groupId readonly property of the MediaDeviceInfo interface returns a DOMString that is a group identifier. Two devices have the same group identifier if they belong to the same physical device; for example, a monitor with both a built-in camera and microphone.

Syntax

var groupID = mediaDeviceInfo.groupId;

Value

A DOMString which uniquely identifies the group of related devices to which this device belongs.

Specifications

Examples

In this example, we assemble a list of the devices which are part of the same group as a given device. This might be used to produce a user interface that gathers associated devices together for presentation purposes, or to make it easy for the user to choose to use the built-in camera and microphone on the same display at the same time.

const getDeviceGroup = mainDevInfo => {
  let devList = [];

  navigator.mediaDevices.enumerateDevices()
  .then(devices => {
    devices.forEach(device => {
      if (device.groupId === mainDevInfo.groupId) {
        devList.push(device);
      }
    });
  });

  return devList;
};

The getDeviceGroup() function takes as input the MediaDeviceInfo object describing the device for which a group list is to be built. The function starts by initializing the result array, devList, to be an empty array.

Then navigator.mediaDevices.enumerateDevices() is called to get the list of all media devices. Once the promise resolves, we walk the list using forEach(). For each device, if its groupId matches the main device's groupId, we push the MediaDeviceInfo object onto the list.

Finally, the list, which now contains a MediaDeviceInfo object for each device in the same group, is returned to the caller.

This could be altered easily to either leave out the passed-in device from the returned list, or to place it at the top of the list, by comparing the two objects' deviceId values, only pushing the device onto the result list if it doesn't match.

This version of the example puts the passed-in device at the top of the result list, then adds any other members of the group that are found:

const getDeviceGroup = mainDevInfo => {
  let devList = [mainDevInfo];

  navigator.mediaDevices.enumerateDevices()
  .then(devices => {
    devices.forEach(device => {
      if ((device.groupId === mainDevInfo.groupId) &&
          (device.deviceId !== mainDevInfo.deviceId)) {
        devList.push(device);
      }
    });
  });

  return devList;
};

Browser compatibility

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