text: 'use strict';
  
  // On this codelab, you will be streaming only video (video: true).
  const mediaStreamConstraints = {
      video: true,
    };
    
    // Video element where stream will be placed.
    const localVideo = document.querySelector('video');
    
    // Local stream that will be reproduced on the video.
    let localStream;
    
    // Handles success by adding the MediaStream to the video element.
    function gotLocalMediaStream(mediaStream) {
      localStream = mediaStream;
      localVideo.srcObject = mediaStream;
    }
    
    // Handles error by logging a message to the console with the error message.
    function handleLocalMediaStreamError(error) {
      console.log('navigator.getUserMedia error: ', error);
    }
    
    // Initializes media stream.
    navigator.mediaDevices.getUserMedia(mediaStreamConstraints)
      .then(gotLocalMediaStream).catch(handleLocalMediaStreamError);