qr scan in javascript

To scan QR codes in JavaScript, we can make use of the getUserMedia() method and the ZXing library. The getUserMedia() method is used to access the user's camera, and the ZXing library is used to decode the scanned QR code.

Here's some sample code to achieve QR scanning in JavaScript:


<!DOCTYPE html>
<html>
  <head>
    <title>QR Scanner</title>
    <script src="https://rawgit.com/zxing-js/library/master/src/index.js"></script>
  </head>
  <body>
    <video id="video" width="320" height="240" autoplay></video>
    <canvas id="canvas" style="display:none;"></canvas>
    <script>
      // Get the video element and canvas element
      var video = document.getElementById('video');
      var canvas = document.getElementById('canvas');
      var context = canvas.getContext('2d');

      // Get user's camera
      if(navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
        navigator.mediaDevices.getUserMedia({ video: true }).then(function(stream) {
          video.srcObject = stream;
          video.play();
        });
      }

      // Decode the QR code
      function decode() {
        context.drawImage(video, 0, 0, canvas.width, canvas.height);
        try {
          var decoded = ZXing.decode(canvas);
          console.log(decoded);
        } catch(err) {
          // QR code not detected
        }

        // Scan again
        requestAnimationFrame(decode);
      }

      // Start decoding QR codes
      requestAnimationFrame(decode);
    </script>
  </body>
</html>
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This code sets up a video element for the stream of the user's camera and a canvas element to draw the scanned QR code on. It then uses the getUserMedia() method to access the camera and sets the video source to the stream. The decode() function then sets up a loop to continuously scan for QR codes using the ZXing library. Whenever a QR code is detected, the decoded result is logged to the console.

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