JsQRScanner：扫描QR码时扫描多次

Question

我正在创建一个Web应用程序，用于使用以下库扫描QR码。 https://github.com/jbialobr/JsQRScanner

每当我尝试扫描QR码时，它就会扫描多次。扫描一次后它不会停止。 Here is live demo

这是我的代码段：-

<script type="text/javascript">
function onQRCodeScanned(scannedText)
{
    var scannedTextMemo = document.getElementById("scannedTextMemo");
    if(scannedTextMemo)
    {
        scannedTextMemo.value = scannedText;
    }
}

//this function will be called when JsQRScanner is ready to use
function JsQRScannerReady()
{
    //create a new scanner passing to it a callback function that will be invoked when
    //the scanner succesfully scan a QR code
    var jbScanner = new JsQRScanner(onQRCodeScanned);
    //reduce the size of analyzed images to increase performance on mobile devices
    jbScanner.setSnapImageMaxSize(300);
    var scannerParentElement = document.getElementById("scanner");
    if(scannerParentElement)
    {
        //append the jbScanner to an existing DOM element
        jbScanner.appendTo(scannerParentElement);
    }        
}