Use onkeypress for multiple types filters from keyboard

[Jsfiddle code][1]

  [1]: https://jsfiddle.net/dandrade78/nsypw8hx/5/

I found this function very cool, simple and effective.This onkeypress code to allow you to accept only certain keys

Therefore, I want to understand the logic and receive examples of how to filter for:

1. numbers only and endlines (no white space)
2. vowels only