Image file validation in NodeJS?

Question

Node.js

How to check if the uploaded file is an image (or something else)?
A simple check of the mimetype or extension is done by simply renaming the file.
Here , a colleague recommends checking some "magic numbers". As far as I understand, this is roughly the same as what the file-type module does , which checks

if (check([0xFF, 0xD8, 0xFF])) {
    return {
      ext: 'jpg',
      mime: 'image/jpeg'
    };
  }

How reliable is such a check?
What prevents an attacker from adding the necessary characters to the beginning of the file?
Plus, one more problem: since the server receives data in the multipart form format and the file is present there not as a stream, but as a File object, you will first have to upload the file, then check it and then delete it if something is wrong - that's it The solution is provided in the link above. It seems to me that this is somehow not very ...
Please share your best practices for checking downloaded files.

Answer 1

Solution "check magic numbers (signatures) before uploading" https://gist.github.com/anonymous/3eb41bad8e9bc7ef... or so https://gist.github.com/anonymous/f8d6fc6544be4e04... if there is something with the file not so, he simply will not write it down anywhere.

Answer 2

usually imghdr
with broken jpegs works well, but not 100%, alas