Regex to check if the first character is uppercase

Question

I\'m trying to check that the first character of a username is capital, the following can be letters or numbers and at most 20 characters long. Can someone explain why my synta

Answer 1

Why can't you let the poor users pick their own usernames? What you should do is convert all caps to lowercase.

"User Name".toLowerCase();

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But if you are truly evil, you should change that z to a Z:

/^[A-Z][A-Za-z0-9_-]{3,19}$/

Answer 2

Your first Z is not a capital Z.

/^[A-Z][a-z0-9_-]{3,19}$/

Answer 3

Your first character needs to be A-Z, not A-z

So

/^[A-z][a-z0-9_-]{3,19}$/

Should be

/^[A-Z][a-z0-9_-]{3,19}$/

Answer 4

I would do it like this:

var firstChar = strToCheck.substring(0, 1);

if (firstChar == firstChar.toUpperCase()) {
    // it is capital :D
}

Answer 5

You have a typo, the first z should be a capital -

/^[A-Z][a-z0-9_-]{3,19}$/