Detect User Media Devices and Permission

user_media_detector.js

class UserMediaDetector {

  // Returns info on all user media devices in successful promise resolve.
  getDevices() {
    return new Promise((resolve, reject) => {
      if (!navigator.mediaDevices || !navigator.mediaDevices.enumerateDevices) {
        reject(Error("UserMediaDetector getDevices failed: enumerateDevices is not supported"));
        return;
      }

      navigator.mediaDevices.enumerateDevices()
        .then(devices => {
          resolve(devices.map(
            ({ deviceId, groupId, kind, label }) => ({ deviceId, groupId, kind, label })
          ));
        })
        .catch(reject);
    });
  };

  // Returns permitted status of given user media kind in successful promise resolve.
  permitted(kind) {
    return new Promise((resolve, reject) => {
      if (!kind || !Object.values(UserMediaDetector.Kinds).includes(kind)) {
        reject(Error(`UserMediaDetector permitted failed: kind ${kind} is not supported`));
        return;
      }

      this.getDevices()
        .then(devices => {
          // Note: The presence of a `label` on a device indicates that it
          //   the device is active or persistent permissions are granted.
          const permitted = !!devices.find(
            device => device.kind === kind && !!device.label
          );

          resolve(permitted);
        })
        .catch(reject);
    });
  };

  // Returns boolean value designating if all given media kinds are permitted in successful promise resolve.
  permittedAll(kinds = Object.values(UserMediaDetector.Kinds)) {
    return new Promise((resolve, reject) => {
      const kindsArray = Array.isArray(kinds) ? kinds : Array.of(kinds);
      const promises = kindsArray.map(kind => this.permitted(kind));

      Promise.all(promises)
        .then(permissionStates =>
          resolve(permissionStates.every(isPermitted => isPermitted))
        )
        .catch(reject);
    });
  };
}

UserMediaDetector.Kinds = {
  VideoInput: "videoinput",
  AudioInput: "audioinput",
  AudioOutput: "audioinput"
};

export default UserMediaDetector;

Example usage:

const detector = new UserMediaDetector();
detector.permitted(UserMediaDetector.Kinds.VideoInput)
  .then(weHaveCameraPermission => {
     console.log(weHaveCameraPermission);
  });