How to get file extension on dragenter, before drop?

I am trying to check the type/extension of a file on dragover (before drop) and cannot seem to do this. For some reason the files array has a length of zero on dragover. I have tried using a dragenter event as well with the same result. A lot of people on similar posts say how it is now possible to check the file type after some browser updates but I cannot seem to figure out how.

function checkFile(event: dragEvent){ 
    event.stopPropagation(); 
    event.preventDefault(); 
    const files = event.dataTransfer?.files; 
    console.log(files)
    } 

This function is called from a drop area.

<div ..... @dragover = 'checkFile'>