print concated pdfs

gistfile1.txt

<button
    type="button"
    onclick="printit(['file1.pdf','file2.pdf'])"
>
    Print pdf
</button >


<div id='pdf-viewer'></div >


<script
    src="https://cdnjs.cloudflare.com/ajax/libs/print-js/1.6.0/print.js"
    integrity="sha512-/fgTphwXa3lqAhN+I8gG8AvuaTErm1YxpUjbdCvwfTMyv8UZnFyId7ft5736xQ6CyQN4Nzr21lBuWWA9RTCXCw=="
    crossorigin="anonymous"
    referrerpolicy="no-referrer"
></script >
<script
    src="https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.5.141/pdf.min.js"
    integrity="sha512-BagCUdQjQ2Ncd42n5GGuXQn1qwkHL2jCSkxN5+ot9076d5wAI8bcciSooQaI3OG3YLj6L97dKAFaRvhSXVO0/Q=="
    crossorigin="anonymous"
    referrerpolicy="no-referrer"
></script >
<script
    src="https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.5.141/pdf.worker.entry.min.js"
    integrity="sha512-NJEHr6hlBM4MkVxJu+7FBk+pn7r+KD8rh+50DPglV/8T8I9ETqHJH0bO7NRPHaPszzYTxBWQztDfL6iJV6CQTw=="
    crossorigin="anonymous"
    referrerpolicy="no-referrer"
></script >
<script >
// credit to https://medium.com/@vicky.sharma8127344/print-single-or-multiple-files-with-print-js-and-pdf-js-ab9c8347a309
    const pages = []
    
    var scale = 1;
    const printit = (pdfs) => {
        
        getMultiplePngImagesWithImgTag(pdfs).then((multiplePngImagesWithImgTag) => {
            // Now we have all converted base64 PNGs in image tag and we are ready to render them as html content to print as one single file with Print.js
            printJS({
                printable: multiplePngImagesWithImgTag,
                type: 'image',
                base64: true,
            });
        });
    }
    
    const getMultiplePngImagesWithImgTag = (pdfs) => {
        return new Promise((resolve, reject) => {
            var docPromiseList = [];
            pdfs.forEach((doc, index) => {
                docPromiseList.push(convertBase64PdfToBase64Png(doc));
            });
            
            
            Promise.all(docPromiseList)
                .then((res) => {
                    if (res && res.length) {
                        let doc = [];
                        // These two loops are getting base64 PNG where
                        // first loop is for each document and second loop is for each page of document
                        for (let i = 0; i < res.length; i++) {
                            for (let j = 0; j < res[i].length; j++) {
                                // get all docs in base64PNG in order to print with Print.js with docType as rawHTML
                                // doc = doc.concat(
                                //     `<div style="text-align:center"><img src="${res[i][j]}"/ style="object-fit:cover;"></div><br/>`
                                // );
                                doc.push(res[i][j])
                            }
                            // doc = doc.concat(`<div style="page-break-before: always;"></div>`);
                        }
                        resolve(doc);
                    }
                })
                .catch((err) => {
                    reject(err);
                });
        });
    };
    
    const convertBase64PdfToBase64Png = (pdf_file) => {
        return new Promise((resolve, reject) => {
            pdfjsLib
                .getDocument(pdf_file)
                .promise.then((pdf) => {
                    let totalPages = pdf.numPages;
                    let totalPagePromiseList = [];
                    for (let currentPage = 1; currentPage <= totalPages; currentPage++) {
                        totalPagePromiseList.push(
                            convertEachBase64PdfPageToBase64PngPage(pdf, currentPage)
                        );
                    }
                    
                    Promise.all(totalPagePromiseList)
                        .then((newRes) => {
                            resolve(newRes);
                        })
                        .catch((newError) => {
                            reject(newError);
                        });
                })
                .catch((error) => {
                    // PDF loading error
                    reject(error);
                });
        });
    };
    const convertEachBase64PdfPageToBase64PngPage = (pdf, currentPage) => {
        return new Promise((resolve, reject) => {
            pdf.getPage(currentPage).then((page) => {
                var scale = 1.5;
                var viewport = page.getViewport({scale: scale});
                
                // Prepare canvas using PDF page dimensions
                var canvas = document.createElement('canvas');
                var context = canvas.getContext('2d');
                canvas.height = viewport.height;
                canvas.width = viewport.width;
                
                // Render PDF page into canvas context
                var renderContext = {
                    canvasContext: context,
                    viewport: viewport,
                };
                
                page
                    .render(renderContext)
                    .promise.then(() => {
                        resolve(canvas.toDataURL()); // Returns the content of the current canvas as an image
                    })
                    .catch((error) => {
                        reject(error);
                    });
            });
        });
    };


</script >