How to wait for the file to be saved?

Question

Node.js

I use the library for Node node-fluent-ffmpeg
. I create a file in two formats, wrapped the functions in promises.
I do

Promise.all([makeWebm(file, slug), makeMp4(file, slug)])

And then thenI work with the file further. So, sometimes, after a time, referring to the newly created file, thenI throw an error
Error: ENOENT: no such file or directory,
. The file is naturally there, but at that moment, I believe it is still saved to the disk (having opened the explorer, I see by the icon that the file is still being processed for several milliseconds) . What to do in this case? Well, do not write the same timeout.