I want to upload files with a lowercase extension, even if the user chooses a file with uppercase extension. I use an `<input type="file"/>` for file choosing.

Here's an example:

**Before**  

`(abc.CSV), (def.cSV), (ghi.cSv)`

**After**  

`(abc.csv), (def.csv), (ghi.csv)`

Underneath is a screenshot of the file chooser.

![Screenshot of the file chooser](https://i.stack.imgur.com/61mJS.png)