video.js

const constraints = { "video": { width: { max: 320 } }, "audio" : true };

var theStream;
var theRecorder;
var recordedChunks = [];

function startFunction() {
  navigator.mediaDevices.getUserMedia(constraints)
      .then(gotMedia)
      .catch(e => { console.error('getUserMedia() failed: ' + e); });
}

function gotMedia(stream) {
  theStream = stream;
  var video = document.querySelector('video');
  video.src = URL.createObjectURL(stream);
  try {
    recorder = new MediaRecorder(stream, {mimeType : "video/webm"});
  } catch (e) {
    console.error('Exception while creating MediaRecorder: ' + e);
    return;
  }

  theRecorder = recorder;
  recorder.ondataavailable =
      (event) => { recordedChunks.push(event.data); };
  recorder.start(100);
}

// From @samdutton's "Record Audio and Video with MediaRecorder"
// https://developers.google.com/web/updates/2016/01/mediarecorder
function downloadVideo() {
  theRecorder.stop();
  theStream.getTracks().forEach(track => { track.stop(); });

  var blob = new Blob(recordedChunks, {type: "video/webm"});

  var fd = new FormData();
  fd.append('fname', 'video.webm');
  fd.append('data', blob);
  $.ajax({
    type: 'POST',
    url: 'http://172.16.21.223:3000/api/platform/uploadDocument',
    data: fd,
    processData: false,
    contentType: false
  }).done(function (data) {
    console.log(data);
  });
}