Regex (HTML input pattern) for username

Question

I don't quite understand how to put a regex expression together. I keep trying to combine stuff from similar threads I've seen here, with stuff I've been googling, but I seem to be doing this all wrong.

The only thing I can get right is

[A-Za-z0-9]{6,20}

But when I try to add more to the pattern, it doesn't seem to be working.

NOTE This is using the HTML input pattern attribute. I would appreciate some assistance on this, but I would also appreciate if someone could break down the solution for me, so I could comprehend it a little better.

Username can contain uppercase/lowercase letters
Username can contain numbers
Username can contain underscore, hyphen or period
Username cannot contain spaces
Username cannot contain special characters
Username should be between 6-20 characters in length

I've tried something like this:

[A-Za-z0-9_-]{6,20}\S

I feel like I'm sort of there, but not quite there.

You could match a word character, dot or a hyphen without the \S at the end [\w.-]{6,20} — The fourth bird
– The fourth bird, Commented Oct 19, 2018 at 6:49

JaredPh · Accepted Answer · 2018-11-08 19:10:09Z

2

The following should work:

[A-Za-z0-9\-_\.]{6,20}

To break it down:

A-Z any uppercase char
a-z any lowercase char
0-9 any number
\- hyphen (escaped by '\' depending on what order it is put)
. period

The hyphen doesn't need be escaped depending on the ordering:

[A-Za-z0-9-_.]{6,20}

or

[A-Za-z0-9_.-]{6,20}

should work, while the following shouldn't:

[A-Za-z0-9_-.]{6,20}

In the pattern you were using the \S matches any character that is not whitespace so it would expect an extra character after the 6-20 char string. As no white space (\s) is within the square brackets, the omission means spaces are not allowed; this is the same for special characters.

edited Nov 8, 2018 at 19:10

answered Oct 19, 2018 at 0:41

JaredPh

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1 Comment

Toto Over a year ago

Period doesn't need to be escaped in a character class. [A-Za-z0-9_] can be shortened in \w

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