Alphanumeric JavaScript RegEx for Password Validation

Question

I'm using a regex below to validate password to accept alphanumeric characters only. The regex works if I enter 2 characters one alpha and one number but if more than two characters my regex doesn't work. I want if possible the following results as shown in "Expected Behavior". Can anyone help me rewrite my regex?

JavaScript

 function checkPasswordComplexity(pwd) { var regularExpression = /^[a-zA-Z][0-9]$/; var valid = regularExpression.test(pwd); return valid; }

Current Behavior

Password:Valid a1:true aa1:false aa11:false

Expected Behavior

Password:Valid aa:false (should have at least 1 number) 1111111:false (should have at least 1 letter) aa1:true aa11:true a1a1a1a1111:true

Don't limit characters allowed in password, it only makes them weaker. — Quentin
– Quentin, Commented May 29, 2013 at 12:37

Benjamin Gruenbaum · Accepted Answer · 2013-05-29 12:42:39Z

17

You want to add "one or more", you're currently checking for a letter followed by a number.

Try:

/^[a-zA-Z0-9]+$/

+ means 'one or more'

I also joined the ranges.

Note: I don't understand why you'd want to limit the password to such a small range though, having a wide character range will make your passwords stronger.

Here is a fiddle demonstrating the correct behavior

If you just want to validate that the password has at least one letter and at least one number, you can check like this:

function checkPasswordComplexity(pwd) { var letter = /[a-zA-Z]/; var number = /[0-9]/; var valid = number.test(pwd) && letter.test(pwd); //match a letter _and_ a number return valid; }

edited May 29, 2013 at 12:42

answered May 29, 2013 at 12:35

Benjamin Gruenbaum

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4 Comments

georg Over a year ago

From my understanding, the OP wants the string to have at least one letter AND at least one number.

Jobert Enamno Over a year ago

@Benjamin Gruenbaum thanks for this! It solved my issue. Well with regards to the simplest password complexity it's the needs our our client to have an aphanumeric password only. In fact some local banks here still have alphanumeric password only. Even us still wondering why they haven't switch to complex password. Thanks once again for the help!

Benjamin Gruenbaum Over a year ago

You're welcome. It is my experience, that when working in teams where not everyone is a regex wiz, it is better to avoid things like look-aheads and look-behinds unless you are sure people understand them. It is a nice and powerful concept, but it makes code that is unreadable for people who only know the basic regular expressions. Good luck!

Chijioke Ugwuanyi Over a year ago

If the aim of the solution is to validate inputs that contain BOTH letters and numbers then this does not work.

Sameer Rangrez · Accepted Answer · 2013-05-29 12:45:42Z

function checkPasswordComplexity(pwd) { var regularExpression = /^(?=.*[0-9])(?=.*[a-zA-Z])([a-zA-Z0-9]+)$/; var valid = regularExpression.test(pwd); return valid; }

Casimir et Hippolyte · Accepted Answer · 2013-05-29 13:02:31Z

2

You can use this:

/^(?=.*\d)(?=.*[a-z])[a-z\d]{2,}$/i

edited May 29, 2013 at 13:02

answered May 29, 2013 at 12:41

Casimir et Hippolyte

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Comments

tckmn · Accepted Answer · 2013-05-29 12:43:37Z

Try doing this:

var regularExpression = /^[a-zA-Z0-9]+$/;

This means "one or more letter or number."

However, some users might also want to enter symbols (like &*#) in their passwords. If you just want to make sure there is at least one letter and number while still allowing symbols, try something like this:

var regularExpression = /^(?=.*[a-zA-Z])(?=.*[0-9]).+$/;

The (?=.*[a-zA-Z]) is a positive lookahead. This means that it makes sure that there is a letter ahead of it, but it doesn't affect the regex.

The second one will never match, you want /^(?=.*[A-Z]) etc.

M.Athish krishna · Accepted Answer · 2015-02-12 05:34:17Z

{ var pwd=document.getElementById('pwd').value; var reg = /^[a-zA-Z0-9]{8,}$/; var re=reg.test(pwd); alert(re);

}

Toto · Accepted Answer · 2013-05-29 12:41:23Z

I think lookaround aren't supported by javascript, so you can use:

^([a-zA-Z]+\d+)|(\d+[a-zA-Z]+)

But if they are supported:

/^(?=.*\d)(?=.*[a-zA-Z])[a-zA-Z\d]{2,}$/

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