HTML: Barcode Scanner on modern browser

BarcodeScanner.js

/** 
 Barcode Scanner library
 
 @author: Akira TANAKA <tanaka.akira.2006@gmail.com> (http://mint.pepper.jp)
 
 @dependencies:
 + jquery
 + quagga (https://serratus.github.io/quaggaJS/)
 
 ## Usage example:
 
 [html]
  ```
  <script src="https://code.jquery.com/jquery-3.3.1.min.js" integrity="sha256-FgpCb/KJQlLNfOu91ta32o/NMZxltwRo8QtmkMRdAu8=" crossorigin="anonymous"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/quagga/0.12.1/quagga.min.js" integrity="sha256-JDVyLQRqvRSTL/6WaPud93JXpfEdW11zwjqhoNgkGXc=" crossorigin="anonymous"></script>
  <script type="text/javascript" src="./BarcodeScanner.js"></script>
  ...
  <!-- NOTE: `barcodeScanner` the instance name may be changed. It's up to you. -->
  <div id="barcode-scanner" style="display: none; border: 1px solid gray;">
    <div style="background-color: #ccc; padding: 6px 12px;">
      <strong name="title">QRCode Scanner</strong>
      <span name="close" title="Close" style="cursor: pointer; font-weight: bold; float: right;">&times;</span>
    </div>
    <div style="text-align: right; padding: 8px;">
      <span style="cursor: pointer; color: blue;" name="btn-file" onclick="barcodeScanner.startFile(this)">Switch to File Scan</span>
      <span style="cursor: pointer; color: blue;" name="btn-webcam" onclick="barcodeScanner.startWebcam(this)">Switch to Camera Scan</span>
    </div>
    <div name="pane-file" style="padding: 8px 12px 24px 12px;">
      <label>Select a QRCode image:</label>
      <input type="file" name="file" accept="image/png,image/jpg,image/jpeg,image/gif" style="padding: 8px 0px;" onchange="barcodeScanner.scanFile(this)">
    </div>
    <div name="pane-webcam" style="display: none;">
      <video name="video" autoplay></video>
      <canvas name="canvas" style="display: none;"></canvas>
    </div>
    <div>
      <span name="lbl-processing" style="background: navy; color: white; padding: 4px; min-width:100%; font-weight: bold; display: none;">Processing ...</span>
    </div>
    <div>
      <button name="close" style="width: 100%;">&times; Close</button>
    </div>
  </div>
  ```
 [css]
  ```
  #barcode-scanner {
    z-index: 9999;
    position: fixed;
    top: 0;
    margin: 0 auto;
    width: 100%;
    max-width: 360px;
    background-color: #fff;
    box-shadow: 6px 8px 8px rgba(0, 0, 0, 0.3);
  }
  #barcode-scanner video {
    width: 100%;
  }
  ```
 [js]
  ```  
  // create BarcodeScanner instance and put it on global.
  // NOTE: `barcodeScanner` the instance name may be changed. In that case, you must change them on html too.
  window.barcodeScanner = new BarcodeScanner({ rootSelector: "#barcode-scanner", format: "ean_reader" });
  $(document).on("click", "#btn-open-barcode-scanner", function(e) {
    // open BarcodeScanner webcam scanner
    barcodeScanner.open((err, result) => {
      console.log("BarcodeScanner result:", err, result);
      // console.log("BarcodeScanner dataURL:", result.data);
    });
  });
  ```
*/
class BarcodeScanner {
  /**
   * @param rootSelector {String} - a selector of the root element of BarcodeScanner
   * @param format {String} - See https://serratus.github.io/quaggaJS/#decoder Defaults to "code_128_reader".
   * @param debug {Boolean} - OPTION: debug log output. defaults to false.
   */
  constructor({
    rootSelector = "#barcode-scanner",
    format = "code_128_reader",
    debug = false,
  }) {
    this._init({ rootSelector, format, debug });
  }

  _init({
    rootSelector,
    format,
    debug = false
  }) {
    const self = this;
    // if (!QrCode) throw Error("QrCode instance (https://github.com/edi9999/jsqrcode) required");
    if (!Quagga) throw Error("Quagga instance (https://serratus.github.io/quaggaJS/#) required");
    if (!$) throw Error("jquery instance `$` not found");
    // this.qr = new QrCode(); // need to call `global.QrCode = require('qrcode-reader');` on somewhere to bundle it
    this.debug = debug;
    this.rootSelector = rootSelector;
    const $root = $(rootSelector);
    if (!$root || $root.length <= 0) throw Error(`${rootSelector}: BarcodeScanner's root element not found`);
    this.$root = $root;
    this.format = format;
    //
    // -- for file scanner:
    //
    this.$paneFile = $root.find("[name=pane-file]");
    this.$iptFile = this.$paneFile.find("input[name=file]");
    //
    // -- for webcam scanner:
    //
    this.$paneWebcam = $root.find("[name=pane-webcam]");
    this.canvas = $root.find("[name=canvas]")[0];
    if (!this.canvas) throw Error(`canvas[name=canvas] in ${rootSelector} element not found`);
    this.video = $root.find(`[name=video]`)[0];
    if (!this.video) throw Error(`video[name=video] in ${rootSelector} element not found`);
    this.ctx = this.canvas.getContext('2d');
    if (!this.ctx) throw Error("Canvas 2d context not found");
    //
    // common:
    //
    this.$lblProcessing = $root.find("[name=lbl-processing]");
    // "Close" button click
    this.$root.on("click", "[name=close]", function() {
      self._finish(null);
    });
  }

  open(callback) {
    const self = this;
    self.callback = callback;
    self._togglePane("file");
    self.$lblProcessing.css("display", "none");
    self.$root.show();
  }

  _togglePane(pane = "file") {
    const self = this;
    if (pane === "webcam") {
      self.$paneWebcam.show();
      self.$paneFile.hide();
      self.$root.find("[name=btn-webcam]").hide();
      self.$root.find("[name=btn-file]").show();
    } else {
      self.$paneWebcam.hide();
      self.$paneFile.show();
      self.$root.find("[name=btn-webcam]").show();
      self.$root.find("[name=btn-file]").hide();
      const $file = self.$root.find("input[name=file]");
      $file[0].value = null; // init
    }
  }

  /** open the file pane */
  startFile(e) {
    const self = this;
    self._stopWebcam();
    self._togglePane("file");
    self.$lblProcessing.css("display", "none");
  }

  /** start to scan */
  scanFile(e) {
    const self = this;
    self.$lblProcessing.css("display", "inline-block");
    const $file = self.$root.find("input[name=file]");
    const file = $file[0].files[0];
    if (self.debug === true) console.log(`[${self.constructor.name}] selected file:`, file);
    const fileReader = new FileReader();
    fileReader.onload = function(theFile) {
      if (self.debug === true) console.log(`[${self.constructor.name}] fileReader onload:`, theFile);
      const image = new Image();
      image.onload = function() {
        if (self.debug === true) console.log(`[${self.constructor.name}] image onload:`, image);
        // create a canvas in memory:
        const canvas = document.createElement('canvas');
        // canvas needs enough width and height to draw the qrcode image:
        canvas.width = this.width;
        canvas.height = this.height;
        const ctx = canvas.getContext('2d');
        ctx.drawImage(image, 0, 0);

        const dataURL = canvas.toDataURL();
        self._getCodeFromDataURL(dataURL, function(err, code) {
          if (self.debug === true) console.log(`[${self.constructor.name}] Quagga decodeSingle result:`, result);
          return self._finish(code, self.callback, err);
        });
      };
      const dataURL = theFile.target.result;
      if (!dataURL || !dataURL.startsWith("data:image/")) {
        return self._finish(null, self.callback, Error("Invalid Image File."));
      }
      image.src = dataURL;
    };
    fileReader.readAsDataURL(file);
  }

  _getCodeFromDataURL(dataURL, cb) {
    const self = this;
    // NOTE: see: https://serratus.github.io/quaggaJS/
    const config = {
      // "inputStream": {
      //   "size": 800,
      //   "singleChannel": true
      // },
      // "locator": {
      //   "patchSize": "large",
      //   "halfSample": false
      // },
      "decoder": {
        "readers": [{
          "format": self.format,
          "config": {}
        }]
      },
      "locate": true,
      "src": dataURL,
    };
    Quagga.decodeSingle(config, function(result) {
      if (self.debug === true) console.log(`[${self.constructor.name}] Quagga decodeSingle result:`, result);
      const code = (result && result.codeResult) ? result.codeResult.code : null;
      const err = (code === null) ? Error("Invalid Barcode Image.") : null;
      return cb && cb(err, code);
    });
  }

  /** open the webcam pane and start to scan */
  startWebcam(e) {
    const self = this;
    self._togglePane("webcam");
    self.webcamStopped = false;
    // open webcam device
    navigator.mediaDevices.getUserMedia({
      audio: false,
      video: true
    }).then(function(stream) {
      self.stream = stream;
      self.video.srcObject = stream;
      self.video.onloadedmetadata = function(e) {
        // Do something with the video here.
        self.video.play();
        self._snapshot(self.callback);
      };
    }).catch(function(e) {
      if (self.debug === true) console.error(`[${self.constructor.name}] exception occurred on \`startWebcam()\`:`, e);
      self._finish(null, self.callback, e);
    }); // always check for errors at the end.
  }

  _snapshot(cb) {
    const self = this;
    if (self.webcamStopped) return; // NOTE: Don't call the callback!
    // Draws current image from the video element into the canvas
    self.ctx.drawImage(self.video, 0, 0, self.canvas.width, self.canvas.height);

    const dataURL = self.canvas.toDataURL();
    self._getCodeFromDataURL(dataURL, (err, code) => {
      if (!code) {
        setTimeout(() => {
          return self._snapshot(cb); // retry ...
        }, 1000);
      } else {
        return self._finish(code, cb);
      }
    });
  }

  _stopWebcam() {
    const self = this;
    if (self.video) {
      self.video.pause();
      self.video.src = "";
    }
    if (self.stream) {
      // self.stream.getVideoTracks()[0].stop();
      self.stream.getTracks().forEach(track => track.stop());
    }
    self.webcamStopped = true;
  }

  /** `stop` function is always called on end of process. */
  _finish(data, cb, err) {
    const self = this;
    self._stopWebcam();
    self.$root.hide();
    self.$lblProcessing.css("display", "none");
    return cb && cb(err, data);
  }

};

example.html

<!DOCTYPE html>
<html>

<head>
  <title></title>
  <meta charset="utf-8">
  <script src="https://code.jquery.com/jquery-3.3.1.min.js" integrity="sha256-FgpCb/KJQlLNfOu91ta32o/NMZxltwRo8QtmkMRdAu8=" crossorigin="anonymous"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/quagga/0.12.1/quagga.min.js" integrity="sha256-JDVyLQRqvRSTL/6WaPud93JXpfEdW11zwjqhoNgkGXc=" crossorigin="anonymous"></script>
  <script type="text/javascript" src="./BarcodeScanner.js"></script>
  <style type="text/css">
  #barcode-scanner {
    z-index: 9999;
    position: fixed;
    top: 0;
    margin: 0 auto;
    width: 100%;
    max-width: 360px;
    background-color: #fff;
    box-shadow: 6px 8px 8px rgba(0, 0, 0, 0.3);
  }
  #barcode-scanner video {
    width: 100%;
  }
  </style>
</head>

<body>
  <button id="btn-open-barcode-scanner">Open Barcode Scanner</button>
  <div id="result"></div>
  <div id="barcode-scanner" style="display: none; border: 1px solid gray;">
    <div style="background-color: #ccc; padding: 6px;">
      <strong name="title">Barode Scanner</strong>
      <span name="close" title="Close" style="cursor: pointer; font-weight: bold; float: right;">&times;</span>
    </div>
    <div style="text-align: right; padding: 8px;">
      <span style="cursor: pointer; color: blue;" name="btn-file" onclick="barcodeScanner.startFile(this)">Switch to File scan</span>
      <span style="cursor: pointer; color: blue;" name="btn-webcam" onclick="barcodeScanner.startWebcam(this)">Switch to Webcam scan</span>
    </div>
    <div name="pane-file" style="padding: 8px 12px 24px 12px;">
      <label>Select a Barcode image:</label>
      <input type="file" name="file" accept="image/png,image/jpg,image/jpeg,image/gif" style="padding: 8px 0px;" onchange="barcodeScanner.scanFile(this)">
    </div>
    <div name="pane-webcam" style="display: none;">
      <video name="video" autoplay></video>
      <canvas name="canvas" style="display: none;"></canvas>
    </div>
    <div>
      <span name="lbl-processing" style="background: navy; color: white; padding: 4px; min-width:100%; font-weight: bold; display: none;">Processing ...</span>
    </div>
    <div>
      <button name="close" style="width: 100%;">&times; Close</button>
    </div>
  </div>
  <script type="text/javascript">
  // create BarcodeScanner instance
  window.barcodeScanner = new BarcodeScanner({ rootSelector: "#barcode-scanner", format:"ean_reader" });
  $(document).on("click", "#btn-open-barcode-scanner", function(e) {
    // open BarcodeScanner webcam scanner
    barcodeScanner.open((err, result) => {
      console.log("BarcodeScanner result:", err, result);
      // console.log("BarcodeScanner dataURL:", result.data);
      $("#result").text(result);
    });
  });
  </script>
</body>

</html>