I am trying to use Agora.io. Everything was working as it should. Until I add switching between cameras. I'm trying to switch between cameras thanks to the code below. But the problem is that I get this error: Uncaught TypeError: Cannot read properties of undefined (reading 'deviceId')

The error line is in the changeStreamSource() :

deviceId = devices.cameras[deviceIndex].deviceId;

Can you guide me on this?

function changeStreamSource (deviceIndex, deviceType) {
  console.log('Switching stream sources for: ' + deviceType); 
  var deviceId;
  var existingStream = false; 
  if (deviceType === "video") {    
    deviceId = devices.cameras[deviceIndex].deviceId; 
  }  
   
  localStreams.camera.stream.switchDevice(deviceType, deviceId, function(){  
    console.log('successfully switched to new device with id: ' + JSON.stringify(deviceId));
    // set the active device ids
    if(deviceType === "audio") {
      localStreams.camera.micId = deviceId;
    } else if (deviceType === "video") {
      localStreams.camera.camId = deviceId;
    } else {
      console.log("unable to determine deviceType: " + deviceType);
    }
  }, function(){
    console.log('failed to switch to new device with id: ' + JSON.stringify(deviceId));
  });
}