我不是很精通JS或编码。我在网上找到了这个脚本，它应该可以帮助我从一个网站上下载一个受保护的PDF。一切工作正常，pdf自动滚动，直到我到保存功能，这是当我得到这个错误从控制台
Uncaught TypeError: Cannot read properties of undefined (reading 'save') at generatePDF (<anonymous>:59:6) at <anonymous>:105:25
看起来问题命令是这个
doc.save(pdfDocumentName);
这里是完整的代码。我不确定问题出在哪里

let jspdf = document.createElement("script");
jspdf.onload = function () {
    let pdfDocumentName = "Document";
    let doc;

    function generatePDF (){
        let imgTags = document.getElementsByTagName("img");
        let checkURLString = "blob:https://drive.google.com/";
        let validImgTagCounter = 0;
        for (i = 0; i < imgTags.length; i++) {

            if (imgTags[i].src.substring(0, checkURLString.length) === checkURLString){
                validImgTagCounter = validImgTagCounter + 1;
                //console.log(imgTags[i].src);
                let img = imgTags[i];

                let canvas = document.createElement('canvas');
                let context = canvas.getContext("2d");
                canvas.width = img.naturalWidth;
                canvas.height = img.naturalHeight;
                //console.log("Width: " + img.naturalWidth + ", Height: " + img.naturalHeight);
                context.drawImage(img, 0, 0, img.naturalWidth, img.naturalHeight);
                let imgDataURL = canvas.toDataURL();
               // console.log(imgDataURL);

                //let ratio;
                let orientation;
                if (img.naturalWidth > img.naturalHeight){
                    //console.log("Landscape");
                    orientation = "l";
                    //ratio = img.naturalWidth/img.naturalHeight
                }else {
                    //console.log("Portrait");
                    orientation = "p";
                    //ratio = img.naturalWidth/img.naturalHeight
                }

                let scalefactor = 1.335;
                let pageWidth = img.naturalWidth * scalefactor;
                let pageHeight = img.naturalHeight * scalefactor;
               //let imagexLeft = (pageWidth - img.naturalWidth)/2;
               //let imagexTop = (pageHeight - img.naturalHeight)/2;
                if (validImgTagCounter === 1){
                    doc = new jsPDF({
                        orientation: orientation,
                        unit: "px",
                        format: [pageWidth, pageHeight],
                    });
                    doc.addImage(imgDataURL, "PNG", 0, 0, img.naturalWidth, img.naturalHeight);
                }else{
                    doc.addPage([pageWidth, pageHeight] , orientation);
                    doc.addImage(imgDataURL, "PNG", 0, 0, img.naturalWidth, img.naturalHeight);
                }
            }
        }

        pdfDocumentName = pdfDocumentName + ".pdf";
    doc.save(pdfDocumentName);
    }

    let allElements = document.querySelectorAll("*");
    let chosenElement;
    let heightOfScrollableElement = 0;

    for (i = 0; i < allElements.length; i++) {
        if ( allElements[i].scrollHeight>=allElements[i].clientHeight){
            if (heightOfScrollableElement < allElements[i].scrollHeight){
                //console.log(allElements[i]);
                //console.log(allElements[i].scrollHeight);
                heightOfScrollableElement = allElements[i].scrollHeight;
                chosenElement = allElements[i];
            }
        }
    }

    if (chosenElement.scrollHeight > chosenElement.clientHeight){
        console.log("Auto Scroll");

        let scrollDistance = Math.round(chosenElement.clientHeight/2);
        //console.log("scrollHeight: " + chosenElement.scrollHeight);
        //console.log("scrollDistance: " + scrollDistance);

        let loopCounter = 0;
        function myLoop(remainingHeightToScroll, scrollToLocation) {
            loopCounter = loopCounter+1;
            console.log(loopCounter);

            setTimeout(function() {
                if (remainingHeightToScroll === 0){
                    scrollToLocation = scrollDistance;
                    chosenElement.scrollTo(0, scrollToLocation);
                    remainingHeightToScroll = chosenElement.scrollHeight - scrollDistance;
                }else{
                    scrollToLocation = scrollToLocation + scrollDistance ;
                    chosenElement.scrollTo(0, scrollToLocation);
                    remainingHeightToScroll = remainingHeightToScroll - scrollDistance;
                }

                if (remainingHeightToScroll >= chosenElement.clientHeight){
                    myLoop(remainingHeightToScroll, scrollToLocation)
                }else{
                    setTimeout(function() {
                        generatePDF();
                    }, 1500)
                }

            }, 500)
        }
        myLoop(0, 0);

    }else{
        console.log("No Scroll");
        setTimeout(function() {
            generatePDF();
        }, 1500)
    }

};
jspdf.src = 'https://cdnjs.cloudflare.com/ajax/libs/jspdf/1.5.3/jspdf.debug.js';
document.body.appendChild(jspdf);

我会感激任何和所有的帮助！