regular expression to allow only specific numbers

Question

I am looking to have a regular expression that allows only specific numbers to be entered, e.g. 2,4,5,6,10,18

I tried something like

"'2'|'4'|'5'|'6'|'10'|'18'"

and anything that i typed failed the regex and then the computer pointed its finger at me and laughed.

where am i going wrong?

Answer 1

The single quotes are unnecessary. The regex you are looking for is: ^(2|4|5|6|10|18)$.

The symbols ^ and $ denote the start and the end of the line, to prevent 121 from matching (since it contains 2).