JSFiddle - React, Tailwind, and code Playground

HTML

Vid1:
  <video id="vid1" width="100" height="100"></video>
  Vid2:
  <video id="vid2" width="100" height="100"></video>
  
  <br/><br/><br/>
  <div id="but_restart">Restart vid2</div>

JavaScript

var stream2;
var vid1 = document.getElementById('vid1');
var vid2 = document.getElementById('vid2');
var but  = document.getElementById('but_restart');

vid1.autoplay = true;
vid2.autoplay = true;

// Start stream1 which will stay alive for the rest of these tests
start(vid1, function(strm) {
	//
});

but.onclick = function() {
  // Stop old strean2
  if(stream2)
    stop(vid2, stream2);
  // Start new strean2
  start(vid2, function(strm) {
    stream2 = strm;
  });
};

function start(videl, cbGotStream) {
  navigator.mediaDevices.getUserMedia({video:true, audio:false})
  .then(function(stream) {
      console.log('got local media');
      videl.src = window.URL.createObjectURL(stream);
      cbGotStream(stream);
    });
}
function stop(videl, stream) {
  videl.src = '';
  var tracks = stream.getTracks();
  for(var i = 0; i < tracks.length; ++i) {
    tracks[i].stop();
  }
}