// function getWebCapVideo() that will take an # as parameter

function getWebCapVideo(id) {

  // grab webcam video and display it in the video element

  navigator.mediaDevices

    .getUserMedia({ video: true })

    .then(function (stream) {

      var video = document.querySelector(id);

      video.srcObject = stream;

      video.onloadedmetadata = function (e) {

        video.play();

      };

    })

    .catch(function (err) {

      console.log("An error occurred: " + err);

    });

}

// use

getWebCapVideo("#cameraPreview");