using a regular expression to only allow users to type in numbers in a html textbox.

Hi experts,

I created this JavaScript example:

https://jsfiddle.net/wm0peLb6

This example works fine, but this example uses key codes. The textbox only allows a user to type in numbers in the textbox.

I'm trying to created this same example but instead of using keycodes i want to use a Regular Expression to only allow numbers to be typed in.

Anyone know how I revise this example to use a regular expression?