Nothing but zeroes after the first zero-CodePudding

Using regular expressions, how can I make sure there are nothing but zeroes after the first zero?

ABC1000000 - valid
3212130000 - valid
0000000000 - valid
ABC1000100 - invalid
0001000000 - invalid

The regex without validation would be something like this - [A-Z0-9]{10}, making sure it is 10 characters.

CodePudding user response：

You could update the pattern to:

^(?=[A-Z0-9]{10}$)[A-Z1-9]*0 $

The pattern matches:

^ Start of string
(?=[A-Z0-9]{10}$) Positive looakhead, assert 10 allowed chars
[A-Z1-9]* Optionally match any char of [A-Z1-9]
0 Match 1 zeroes
$ End of string

Regex demo

If a value without zeroes is also allowed, the last quantifier can be * matching 0 or more times:

^(?=[A-Z0-9]{10}$)[A-Z1-9]*0*$

CodePudding user response：

You can use a lookahead to match a string of 10 characters. Then, just match everything but 0 from the start of the string, then only zeroes until the end of the string:

^(?=.{10}$)[^0]*0 $

This works for all of your test cases. You can change the one to many symbol after the last 0 to zero or many (*) if you don't require 0's.

var re = /^(?=.{10}$)[^0]*0 $/mi;

console.log(re.test('ABC1000000'));
console.log(re.test('3212130000'));
console.log(re.test('0000000000'));
console.log(re.test('ABC1001000'));
console.log(re.test('0001000000'));
console.log(re.test('32121300000')); // too short
console.log(re.test('321213000')); // too long

CodePudding user response：

If you want to find strings like that within other text (rather than anchored with ^ and $):

(?<![A-Z0-9])(?=[A-Z0-9]{10}(?:[^A-Z0-9]|$))([^0]*0*(?=(?:[^A-Z0-9]|$)))

Demo