...
The regular expression in the example above validates the union of the four pieces of logic:
09:.* validates 09:00-09:59
1.:.* validates 10:00-19:59
20:.* validates 20:00-20:59
21:00 validates 21:00
...
Example #2: Validating that a participant inputs a zip code that is 5 numbers ranging from 0-9:
([0-9]{5})
[0-9] = a char in range 0-9 (inclusive)
{5} = repeat the prior criteria 5 times
Example #3: Validating that a kit ID is either 6 digits or 6 digits with a space in the middle
(e.g., 012 293 or 012293):
[0-9]{3} ?[0-9]{3}
[0-9] = a char in range 0-9 (inclusive)
{3} = repeat the prior criteria 3 times
“ ?” = 0 or 1 spaces (? = match 0 or 1 of the preceding character, which in this case is a blank space)
Example #4: Validating DOB with the format MM/DD/YYYY:
^[0-9]{2}[/][0-9]{2}[/][0-9]{4}$
[0-9] = a char in range 0-9 (inclusive)
{2} = repeat the prior criteria 2 times
{4} = repeat the prior criteria 4 times
[/] = insert / symbol
^ . . . $ = complete match in a message (instead of partial match)