How to scan QR-code using JavaScript

Scan.html

	<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
	<script src="https://rawgit.com/schmich/instascan-builds/master/instascan.min.js"></script>

  <video id="preview" height="160" style="border: 1px solid black"></video>
    <p id="results"></p>
    <script type="text/javascript">
      let scanner = new Instascan.Scanner({ video: document.getElementById('preview') });
      scanner.addListener('scan', function (content) {
        $('#results').html(content);
      });
      Instascan.Camera.getCameras().then(function (cameras) {
        if (cameras.length > 0) {
          scanner.start(cameras[0]);
        } else {
          alert('No cameras found.');
        }
      }).catch(function (e) {
        alert(e);
      });
    </script>