Regular expression for csv of numbers less than 1,000

Question

I am going to use JavaScript to validate a string that needs to be:

• Only digits and commas
• Can't end or start with a comma
• Each number between the commas has to less than 1,000
• No negatives
• No periods, just digits and commas

I tried:

\d{1,3}(,{1,3})*

But it doesn't quite do what I mentioned above.

Answer 1

You can use the following regular expression to match numbers starting at new line, having comma separator between groups of 3 digits.

^(?:\d{1,3}(?:(,?)\d{3})?(?:\1\d{3})*)$

Details:

• ^ asserts position at start of a line.
• ?: Match expression but do not capture it.
• \d matches a digit (equal to [0-9]).
• {1,3} Quantifier — Matches between 1 and 3 times, as many times as possible, giving back as needed.
• Capturing Group (,?) matches the character , literally.
• \1 matches the same text as most recently matched by the 1st capturing group.
• {3} Quantifier — Matches exactly 3 times.
• $ asserts position at the end of a line.