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 syntax is wrong?

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

Your description doesn't match your regex. According to your description, you'd want something more like this `/^[A-Z][a-zA-Z0-9]{1,19}$/` — RightSaidFred, Nov 25 '11 at 22:08

score 32 · Accepted Answer · answered Nov 25 '11 at 21:55

32

Your first Z is not a capital Z.

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

answered Nov 25 '11 at 21:55

BoltClock

700,868
160
1,392
1,356

I tried this, but for some reason the first letter isn't being recognized as capital. I entered "ssss" and it matched. – Sam Nov 25 '11 at 22:14
Actually never mind, I was using a regex expression tool incorrectly. – Sam Nov 25 '11 at 22:19

score 10 · Answer 2 · edited May 23 '17 at 10:30

10

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();

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

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

edited May 23 '17 at 10:30

Community

1
1

answered Nov 25 '11 at 21:57

Mateen Ulhaq

24,552
19
101
135

2

I'd say this is the perfect answer to spend my last vote on :) – Adam Rackis Nov 25 '11 at 22:00

score 7 · Answer 3 · edited Nov 25 '11 at 21:59

7

I would do it like this:

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

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

edited Nov 25 '11 at 21:59

Mateen Ulhaq

24,552
19
101
135

answered Nov 25 '11 at 21:58

BronzeByte

685
1
7
11

1

Anything that avoids a regex is ok in my book. – dumdum Nov 25 '11 at 22:03
@muntoo it's just about the idea, of course you should check it :P But you could also disallow spaces, solved :P – BronzeByte Nov 25 '11 at 23:10

score 6 · Answer 4 · answered Nov 25 '11 at 21:55

6

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}$/

answered Nov 25 '11 at 21:55

Adam Rackis

82,527
56
270
393

score 0 · Answer 5 · answered Nov 25 '11 at 21:56

0

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

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

answered Nov 25 '11 at 21:56

ipr101

24,096
8
59
61

Regex to check if the first character is uppercase

5 Answers5

Linked