Javascript regex for username containing letters, numbers and one hyphen

Question

I'm going to check the username via both JavaScript then PHP.

The username can contain English letters, numbers and one hyphen (-).

The username cannot be started with hyphen (-).

The username cannot be finished with hyphen (-).

The username cannot be started with numbers.

The username cannot contain more than one hyphen (-).

The username cannot be shorter than 6 and longer than 20.

abc123 is correct.
abc-123 is correct.
ab12 is wrong: username is shorter than 6 character.
-abc123 is wrong: username is started with hyphen.
abc123- is wrong: username is finished with hyphen.
ab-12-c3 is wrong: username contains more than one hyphen.
123abc is wrong: username is started with numbers.

What is the problem you are facing? What have you tried? – Amadan Aug 07 '15 at 07:32 — Amadan, Aug 07 '15 at 07:32
Could you show us what have you tried already? – Maksim Solovjov Aug 07 '15 at 07:32 — Maksim Solovjov, Aug 07 '15 at 07:32

score 4 · Accepted Answer · answered Aug 07 '15 at 07:43

4

You can use

^(?!\d)(?!.*-.*-)(?!.*-$)(?!-)[a-zA-Z0-9-]{6,20}$

See demo

Explanation:

^ - Match at the beginning
(?!\d) - Do not match if the string starts with a digit
(?!.*-.*-) - Do not match if the string has 2 hyphens in the string
(?!.*-$) - Do not match if the string ends with a hyphen
(?!-) - Do not match if the string starts with a hyphen
[a-zA-Z0-9-]{6,20} - Match 6 to 20 characters from the range specified
$ - Assert the end of string.

answered Aug 07 '15 at 07:43

Wiktor Stribiżew

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@Milad: Does it work for you? Is anything unclear? – Wiktor Stribiżew Aug 07 '15 at 07:45
1

It works and it's really clear and instructive. appreciate it. – Milad Rahimi Aug 07 '15 at 07:56

score 2 · Answer 2 · answered Aug 07 '15 at 07:49

2

You need to use a lookahead based regular expression:

/^(?=.{6,20}$)[a-z][a-z0-9]+(?:-[a-z0-9]+)?$/i

A logical approach using JavaScript, would be:

function _isvalid(str) {
   var re = /^[a-z][a-z0-9]+(?:-[a-z0-9]+)?$/i
   return ((str.length > 5) && (str.length < 21) && re.test(str))
}

answered Aug 07 '15 at 07:49

hwnd

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thank you @hwnd so much. – Milad Rahimi Aug 07 '15 at 07:59

Javascript regex for username containing letters, numbers and one hyphen

2 Answers2