Question

I need a regex that can match a string of numbers from 1 to 1000 separated by commas.

eg : 12,56,100,190,900,1000

I am using javascript on the front end and php on the back end for validation. Ideally, I need a common regex, which will work for both.

Answer 1

If you want to match the entire line, than something like this should do:

^([1-9][0-9]{0,2}|1000)(,([1-9][0-9]{0,2}|1000))*$

Depending on your requirements, you may also want to allow whitespace in the beginning, end, and/or after commas.

This will allow whitespace in the beginning:
^\s*([1-9][0-9]{0,2}|1000)(,([1-9][0-9]{0,2}|1000))*$

This will allow whitespace at the end:
^([1-9][0-9]{0,2}|1000)(,([1-9][0-9]{0,2}|1000))*\s*$

This will allow whitespaces after commas:
^([1-9][0-9]{0,2}|1000)(,\s*([1-9][0-9]{0,2}|1000))*$

Combine these to your liking.

EDIT 2: If you want to allow a comma in the binning or at the end, then your regex becomes

^,?([1-9][0-9]{0,2}|1000)(,\s*([1-9][0-9]{0,2}|1000))*,?$

Here, ,? means that you can have 0 or 1 comma.

EDIT: explanation, as requested:

• ^ in the beginning and $ at the end are start/end of input marks – they ensure that we test the entire input
• Parentheses work just as you would expect them
• [1-9] matches a digit 1 through 9, similarly [0-9] matches a digit 0 through 9
• {0,2} indicates that the previous part (in our case [0-9]) is present between 0 and 2 times
• | is a logical OR – either part before it matches or the part after it

Thus in the first set of parentheses we match digit 1 to 9 followed by 0, 1 or 2 digits 0 to 9 – this gives us numbers between 1 and 999 – or we match 1000.

Then we match a comma followed by the same block as described above – and this lot is matched 0 or more times – as indicated by * character after the parentheses.