Question

I am trying to write a regular expression that allows decimals with or without commas.

I have –

^[0-9]*((,\d{3})?(,\d{3})?(,\d{3})?)*(\.[0-9]{1,10})?$ 

which seems to work in reg ex tester, but when I put it in my code it doesn’t work. If fails for 1,000.00, but not 1,000

I need it to accept 1, 1000, 1000.00, 1,000,000.123, 1223.456, 1,000,123.928 etc.

Answer 1

This regex seems to work (try it here), but it is slightly overcomplicated, while at the same time allowing inconsistent use of , (i.e 12345,789,000.123). This should solve that problem:

^\d{1,3}(?:(,?)\d{3}(?:\1\d{3})*)?(?:\.\d{1,10})?$

By using a backreference (\1) you can make sure that the , is either always used, or never.

Making digits in front of the . optional while still requiring them in front of a , is also possible, but slightly more complicated:

^(?:\d{1,3}(?:(,?)\d{3})?)?(?:\1\d{3})*(\.\d{1,10})?$