regex to detect leading zeros and check the lenght from 0 to 12 digits.

Question

Hi I have a javascript function that checks for signed integer with 0 to 12 length, i also want to see if there are any leading 0's like 0012 should return false.

function sInteger0to12(str) {
    str = str.replace(/^\s+|\s+$/g, '');
    return /^[-+]?\d{0,12}$/.test(str);
}

any help will be appreciated.

Answer 1

I'm assuming that the following should match:

1
+1
-1
0
-123456789012
<empty>

And these should fail:

-
+
01
-01
1234567890123
00
+0
-0

If you disagree with my decisions above, please let me know and I will try to fix the regex.

Here's a regex you can use:

/^([-+]?[1-9]\d{,11}|0)?$/

Answer 2

Like this:

 /^[-+]?[1-9]\d{0,11}$/

You'll need to check for '0' separately.

Answer 3

You need to cover three cases

1. an empty string
2. a single 0
3. a no zero padded 1 to 12 digit number

these cases equate to

1. ^$
2. ^0$
3. ^[+-]?[1-9]\d{0,11}$

which adds up to

^()|(0)|([+-]?[1-9]\d{0,11})$