I am using this ^[a-z0-9_-]{3-20}$ regex for validating usernames..

my requirements

• it should be between 3-20
• it should not have special chars except hyphen and underscore
• it should start with alphabet

what is problem with this regex

• it checks for 3-20 but it also returns true when string have special chars between 3-20
• it works (return false {what is expected}) when special chars between 1-3 but it fails(return true {what is not expected}) when special chars between 3-20...

I am using yii framework and default rule match pattern... is it yii fault ...?

I am using this ^[a-z0-9_-]{3-20}$ regex for validating usernames..

my requirements

• it should be between 3-20
• it should not have special chars except hyphen and underscore
• it should start with alphabet

what is problem with this regex

• it checks for 3-20 but it also returns true when string have special chars between 3-20
• it works (return false {what is expected}) when special chars between 1-3 but it fails(return true {what is not expected}) when special chars between 3-20...

I am using yii framework and default rule match pattern... is it yii fault ...?

• javascript
• regex

1 Answer 1

you can use this:

/^[a-z][a-z0-9_-]{2,19}$/i

You must use a , to write a range in curly brackets quantifiers. I have put an only letter character class at first to follow your specifications (begin with a letter), thus I decrement the quantifier to {2,19}

I assumed you allow uppercase letters and i add an i modifier, but you can remove it if you only allow lowercase letters.

Note that you can write this regex like that:

/^[a-z][\w-]{2,19}$/i

since \w stand for [a-zA-Z0-9_]