Question

So, I have this if statement:
if (String(val).search(/^((\d+(((\,\d{3,})+)?)(\.\d+)?)|(\.\d+))$/) !== -1)

Which says (as far as I am aware):
The string must either start with at least one digit, or a ..
If the string starts with a digit there can optionally be commas in the string, as long as the commas are followed by at least three digits.
If the string has a . in it, it must be followed by at least one digit.
There can be only one .

So, strings like:

5
5.00
5000
5,000
5000.00
5,000.00

Will all return true

But strings that contain anything but 0-9 , . or are malformed will return false.
so strings like this:

5,00
5,00.00
5.00.00
a5

Now, the above works, but I am wondering if there is any way to simplify it?

Answer 1

You can remove some redundant parenthesis:

^(\d+((\,\d{3,})+)?(\.\d+)?|\.\d+)$

And something like (( ... )+)? can be replaced by: ( ... )*, so the final regex might look like this:

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

And if you’d like to reject input like:

50000,000,000.0

and only allow for:

5,000,000.0
50,000,000.0
500,000,000.0

Then do something like this:

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