Feature request: Browser support

[Munawwar]

Hi. First off, thanks for this project. It's amazing.
It would be nice to make this library browser compatible (instead of relying on fs) so that for small PDFs a server solution isn't needed.

I've managed to make (a subset) of your code, browser compatible.

So instead of reading from file I used fetch() API:

const doc = new pdf.Document();

const inputFileBuffer = await (await fetch(url).arrayBuffer();
const ext = new pdf.ExternalDocument(inputFileBuffer);
doc.setTemplate(ext);
doc.addPagesOf(ext);

And instead of writing to file one can force browser download:

doc.end();

const buffer = await readableToBuffer(doc);
downloadBuffer({
    buffer,
    fileName: 'merged.pdf',
});

readableToBuffer & downloadBuffer implementations:

async function readableToBuffer(readable) {
  const chunks = [];
  for await (const chunk of readable) {
    chunks.push(chunk);
  }
  return Buffer.concat(chunks);
}


function downloadBuffer({ buffer, fileName }) {
  // Create an invisible A element
  const a = document.createElement('a');
  a.style.display = 'none';
  document.body.appendChild(a);


  // Set the HREF to a Blob representation of the buffer to be downloaded
  a.href = window.URL.createObjectURL(
    new Blob([buffer]),
  );
  // Use download attribute to set set desired file name
  a.setAttribute('download', fileName);


  // Trigger the download by simulating click
  a.click();


  // Cleanup
  window.URL.revokeObjectURL(a.href);
  document.body.removeChild(a);
}

The result: Merging small PDFs is amazingly fast. Faster than "pdf to canvas to jpeg/png" based solutions proposed out there in the web.

[erickximenes]

Do you have the complete code to share?

[Munawwar]

@ZaunSupremoXV I have full code at https://github.com/Munawwar/merge-pdfs-on-browser/blob/master/public/pdfjs-approach/pdf-merger-js-adapted.js
But I later didn't go with this approach, as some specific PDFs crashed while merging (which I think I reported to pdfjs and is now fixed). So I went with server-side solution with PDFtk. However someone here can pursue taking that code and merging it into this repo.

[erickximenes]

Thanks @Munawwar

[mojoaxel]

Implemented in #51 by @DanMHammer

released in pdf-merger-js@3.2.0 🎉