Matching numbers with regular expressions — only digits and commas

Question

I can\'t figure out how to construct a regex for the example values:

123,456,789
-12,34
1234
-8

Could you help me?

Answer 1

Try this:

^-?\d{1,3}(,\d{3})*(\.\d\d)?$|^\.\d\d$

Allows for:

1
12
.99
12.34 
-18.34
12,345.67
999,999,999,999,999.99