Question

I need to create a regex expression for the following scenario.

It can have only numbers and only one dot or comma.

First part can have one to three digits.
The second part can be a dot or a comma.
The third part can have one to two digits.

The valid scenarios are

123,12
123.12
123,1
123
12,12
12.12
1,12
1.12
1,1
1.1
1

I came up so far with this expression

\d{1,3}(?:[.,]\d{1,2})?

but it doesn’t work well. For example the input is 11:11 is marked as valid.

Answer 1

You need to put anchors around your expression:

^\d{1,3}(?:[.,]\d{1,2})?$

^ will match the start of the string

$ will match the end of the string

If those anchors are missing, it will partially match on your string, since the last part is optional, means on “11:11” it can match on the digits before the colon and a second match will be on the digits after the colon.