Unexpected Javascript RegExp behavior [duplicate]

Answer 1

Per documentation: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/RegExp/test#Description

test called multiple times on the same global regular expression instance will advance past the previous match.

You can confirm this behavior:

var test = new RegExp( '[0-9]', 'g' );
test.test('01'); //true
test.test('01'); //true
test.test('01'); //false

It doesn't make sense to use the g flag if all you want is to confirm a single match against various strings.