Merging pdfs in a loop results in a blank page

[jerry-flam]

I am using the following code to merge the pdfs of a folder, inspired from this comment: #24 (comment)

const path = require('path');
const glob = require('glob');
const PDFMerger = require('pdf-merger-js');

const merger = new PDFMerger();
const pdfsFolder = path.join(__dirname, 'files');

glob(pdfsFolder + '/*.pdf', {}, (_err, files) => {
  files.forEach((file) => {
    merger.add(file);
  });
  merger.save('merged.pdf');
});

The result is an empty pdf file.

On the other hand, the following works fine:

const PDFMerger = require('pdf-merger-js');

const merger = new PDFMerger();
const pdfsFolder = path.join(__dirname, 'files');

(async () => {
  await merger.add(pdfsFolder + '/file1.pdf');
  await merger.add(pdfsFolder + '/file2.pdf');
  await merger.save('merged.pdf');
})();

Am I missing something or it is a bug?

Software versions:
node: v16.17.0
glob: v8.0.3
pdf-merger-js: v4.1.0

[jerry-flam]

Here is a repo reproducing the issue: https://github.com/jerry-flam/pdf-merger-js-issue-98

[mojoaxel]

I had a quick look. It looks to me like you forgot to await the (newly introduced) add promise.

Try this:

glob(pdfsFolder + '/*.pdf', {}, async (_err, files) => { 
  for (let file of files) { 
    await merger.add(file);
  });
  await merger.save('merged.pdf');
});

[jerry-flam]

Thank you very much! This solved it!