Regex valid numbers with thousand separator

Question

I'm doing a validation in asp.net textbox, and the textbox only allows user to input number

i.e.

valid numbers:

1234
12.345
12,345,678.231
12,345,678

invalid numbers:

-1234
12.23.45.67
12,
12,34,56
12,345,6

I'm trying to use a regex to validate the user's input on client side with the below regex:

^(?=.+)(?:[1-9]\d*|0)?(?:\.\d+)?$

The problem is:

the above regex only consider below as valid:

1234
12.345

How to modify the above regex to check if the thousand separator being entered into the correct place or not?

Answer 1

this seems to work ^\d+(,\d{3})*(\.\d+)?$
Demo