Javascript String Character Checking

Question

What would be the best way to check that a javascript string is at least four characters long, contains at least one lowercase letter, one uppercase letter and a digit?

What methods have you tried already? What problems did you face? — Lix, Apr 18 '13 at 11:16

score 1 · Accepted Answer · edited May 23 '17 at 11:43

1

Testing for lowercase letters has already been covered elsewhere:

function hasLowerCase(str) {
    return (/[a-z]/.test(str));
}

It's trivial to modify that to implement hasUpperCase and hasDigits.

Once you have written these functions, you can just check that:

if( hasLowerCase(passwd) && hasUpperCase(passwd) && hasDigits(passwd) ) {
    // Its a valid password!
}

If you use it in many places, consider making a new function:

function isPasswordValid(str) {
    return hasLowerCase(passwd) && hasUpperCase(passwd) && hasDigits(passwd);
}

Which you can further use like:

if( isPasswordValid("passwd") ) {
    // ...
}

edited May 23 '17 at 11:43

Community

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answered Apr 18 '13 at 11:16

jsalonen

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I already looked at regular expressions and that example but am not too familiar with regex. Would it possible to have one regex statement or would I need three statements - one for the lower, upper and digit cases, then check that all three are true? – user1334130 Apr 18 '13 at 11:19
Yes you can do exactly that! – jsalonen Apr 18 '13 at 11:20
OK so I'll need a check for all three. – user1334130 Apr 18 '13 at 11:20
Testing for all three in one regex is not a good idea because you don't know what order they're in. – ColBeseder Apr 18 '13 at 11:27
Wow stop! I definitely meant using THREE regexes just for this exactly same reason! Sorry for ambiguity! – jsalonen Apr 18 '13 at 11:29

ColBeseder · Answer 2 · 2013-04-18T11:23:47.810

Here's a quick validation function:

function validate(str) {
    return str.length > 3 && /[a-z]/.test(str) && /[A-Z]/.test(str) && /[0-9]/.test(str) ;
}

It checks the length and then runs regular expressions looking for lowercase, uppercase and numbers (in that order). If all are true (length > 3 and has lowercase and has uppercase and has a number) it returns true. Otherwise, it returns false.

use it like this:

validate("aaaa")  // returns false
validate("aA1")   // returns false
validate("aA12")  // returns true

rab · Answer 3 · 2013-04-18T11:36:36.007

0

I wrote a function, same like ColBeseder .added a type checking string

function check( str ){

    return ( typeof str == 'string') &&
           ( str.length >= 4 ) &&
           /[a-z]/.test( str ) &&
           /[A-Z]/.test( str ) && 
           /[0-9]/.test( str )

}

and call its as check('AAA1a') , which returns a boolean

edited Apr 18 '13 at 11:36

answered Apr 18 '13 at 11:26

rab

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Javascript String Character Checking

3 Answers3