# Using Phone Cameras with `getUserMedia`

**Multi camera cases**

Even cheap phones can have multiple cameras, but the default camera for `getUserMedia` is probably not the "primary", and may lack focus feature, which is important for scanning barcodes.

const changeCamera = (video, {index} = {}) => {
  const devices = (await navigator.mediaDevices.enumerateDevices()).filter(
    device => device.deviceId && device.kind === 'videoinput'
  )
  if (video.srcObject && devices.length === 1) {
    return
  }
  const lastIndex =
    devices.findIndex(device => device.deviceId === ref.deviceId) || 0
  ref.deviceId = devices[index ?? (lastIndex + 1) % devices.length].deviceId
  await ref.request
  if (video.srcObject) {
    const tracks = video.srcObject?.getVideoTracks?.() || []
    tracks.forEach(track => track.stop())
  }
  ref.request = navigator.mediaDevices.getUserMedia(
    next
      ? {focusMode: 'continuous', deviceId: next}
      : {focusMode: 'continuous', facingMode: 'environment'}
  )
  const stream = await ref.request
  video.srcObject = stream
}