Question

165

Javascript regex to validate if number begins with leading zero

rated 0 times [ 167] [ 2] / answers: 1 / hits: 32462 / 11 Years ago, thu, june 6, 2013, 12:00:00

I need to validate some inputs using a regex.

Here are some sample use cases and expected results.

0001     - Matched

001      - Matched

01       - Matched

00.12312 - Matched

000.1232 - Matched

1        - Not matched

20       - Not matched

0.1      - Not matched

0.123123 - Not matched

What would a regex like this look like? If first char is 0 and second char is numerical[0-9] then it is invalid.

I've tried this but it doesn't work.

[0][0-9]

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answered 11 Years ago michaelashelbieh · Accepted Answer

Try this regex:

^0[0-9].*$

It will match anything starting with 0 followed by a digit.

It will match what you call invalid.

The test code shall make it clearer:

var regExp = /^0[0-9].*$/

console.log(regExp.test(0001)); // true

console.log(regExp.test(001)); // true

console.log(regExp.test(01)); // true

console.log(regExp.test(00.12312)); // true

console.log(regExp.test(000.1232)); // true

console.log(regExp.test(1)); // false

console.log(regExp.test(20)); // false

console.log(regExp.test(0.1)); // false

console.log(regExp.test(0.123123)); // false