Question

This regular expresion does not work when I enter 100 for some reason but 100.0 is ok.

^(?!0*(.0+)?$)(\d+|\d*\.\d+)$ 

Any ideas why this is happening?

Answer 1

It’s your negative lookahead which causes the problem:

0*(.0+)?$

The dot in here means any character – you want to escape it:

^(?!0*(\.0+)?$)(\d+|\d*\.\d+)$

Or even simpler with a positive lookahead:

^(?=.*?[1-9])(\d+|\d*\.\d+)$