I used a regular expression to restrict the numbers only between 3.00 to 100.00.But it was allowing the numbers between 100.01 to 100.99

Question

I have a requirement to restrict the numbers between 3.00 to 100.00 I used below expression

^([3-9]|[1-9][0-9]|100)+(\.\d{1,2})?$

The issue with above expression is that, it's allowing 100.01 to 100.99,which should be restricted.It also allows 310 to 399,which needs to restricted.

I used another flavor of same expression

^([3-9]|[1-9][0-9]|100.00)+(\.\d{1,2})?$

Which was working as expected,but we need to enter 100.00 in to pass the regular expression instead of 100.

Is there any way,I can achieve the desired result?

Answer 1

When alternating with the final 100, use negative lookahead for \.\d?[1-9], to ensure that the decimal places, if any, have only 0s.

Your first pattern can also match many repeated digits before the optional decimal (like 333 and 101010) due to the + at the end of the group, so best to remove the + if you only want to match between 3 and 100.

^(?:[3-9]|[1-9][0-9]|100(?!\.\d?[1-9]))(?:\.\d{1,2})?$
                        ^^^^^^^^^^^^^^

https://regex101.com/r/tJd3LQ/1

To permit leading zeros, add 0* right after the ^:

^0*(?:[3-9]|[1-9][0-9]|100(?!\.\d?[1-9]))(?:\.\d{1,2})?$
 ^^