javascript regExp check last character

Question

I'm using this RexExp code var userIdPattern = new RegExp('^([A-z0-9_.]{4,15})$');, I want to check if last character was dot (.) then .test() returns me false:

var userIdPattern = new RegExp('^([A-z0-9_.]{4,15})$');
console.log(userIdPattern.test('Omid.my.')); // -> I need this to be false

and in this case return me true:

userIdPattern.test('Omid.my'); //-> true

Answer 1

Following the update, a more appropriate regex might be:

var userIdPattern = new RegExp('^([A-Za-z0-9\[\]\\^`][A-z0-9_.]{2,13}[A-Za-z0-9\[\]\\^`])$');

That is, if you want to include other special characters in the usernames like 7stud mentioned in his comment and only exclude . and _ from the first and last characters.

Otherwise, to prevent those characters, I would suggest:

var userIdPattern = new RegExp('^([A-Za-z0-9][A-Za-z0-9_.]{2,13}[A-Za-z0-9])$');

Fiddle to test.