Disable automatic upload or upload after data validation

Hello,

I know this is maybe not the best place to post that question but I've already checked and posted a question on stackoverflow, without any answers (same for the people that posted the same question).

What I would like to achieve is basically a data validation before the image get uploaded on the server.

I think it makes no sense to upload the image before doing the data validation as my stockage would be full of useless pictures.

Is it possible with multer? And if so, how would you do that? Thanks a lot!