How to use the @zxing/library.BrowserBarcodeReader function in @zxing/library

constructor(props) {
    super(props);

    const barcodeScannerType = props.barcodeScannerType
      ? props.barcodeScannerType
      : 'qrCode';

    this.state = {
      barcodeScannerType: barcodeScannerType,
    };

    if (barcodeScannerType == 'qrCode') {
      this.reader = new BrowserQRCodeReader();
    } else if (barcodeScannerType == 'barcode') {
      this.reader = new BrowserBarcodeReader();
    } else if (barcodeScannerType == 'datamatrix') {
      this.reader = new BrowserDatamatrixCodeReader();
    } else {
      throw new Error('Unknown barcodeScannerType: ' + barcodeScannerType);
    }
  }

_changeReader = () => {
    const { barcodeScannerType } = this.state;

    this.reader.stopStreams();

    if (barcodeScannerType == 'qrCode') {
      this.reader = new BrowserBarcodeReader();
      this.props.onClose(true);
      this.setState(
        {
          barcodeScannerType: 'barcode',
        },
        () => this._process()
      );
    }
  };