Question

I’m trying to create a regex that accept:
An empty string, a single integer or multiple integers separated by a comma but can have no starting and ending comma.

I managed to find this, but I cannot undertsand how to remove the digit limit

^\d{1,10}([,]\d{10})*$

Answer 1

The thing you posted still requires at least 1 integer, so it won’t match an empty string:

Here is what you need:

^(\d+(,\d+)*)?$

Explaination:

1. put the entire thing in parenthesis and end with a '?' so as to match the empty string.
2. Always start with an integer, so '\d+'. That is 1 or more digit characters ('0'-'9')
3. Then make a set of parenthesis which contains ',\d+' and put an asterisk after it.
   3a. The inside means start with a ‘,’ then an integer.
   3b. The asterisk means repeat everything inside the parenthesis 0 or more times.

Hench the whole thing is either an empty string or start with an integer then repeat zero or more times a string which starts with a comma and ends with an integer