Matching special characters and letters in regex

Question

I am trying to validate a string, that should contain letters numbers and special characters &-._ only. For that I tried with a regular expression.

var pattern = /[a-zA-Z0-9&_\.-]/ var qry = 'abc&*'; if(qry.match(pattern)) {     alert('valid'); } else{     alert('invalid'); } 

While using the above code, the string abc&* is valid. But my requirement is to show this invalid. ie Whenever a character other than a letter, a number or special characters &-._ comes, the string should evaluate as invalid. How can I do that with a regex?

Answer 1

Add them to the allowed characters, but you'll need to escape some of them, such as -]/\

var pattern = /^[a-zA-Z0-9!@#$%^&*()_+\-=\[\]{};':"\\|,.<>\/?]*$/ 

That way you can remove any individual character you want to disallow.

Also, you want to include the start and end of string placemarkers ^ and $

Update:

As elclanrs understood (and the rest of us didn't, initially), the only special characters needing to be allowed in the pattern are &-._

/^[\w&.\-]+$/ 

[\w] is the same as [a-zA-Z0-9_]

Though the dash doesn't need escaping when it's at the start or end of the list, I prefer to do it in case other characters are added. Additionally, the + means you need at least one of the listed characters. If zero is ok (ie an empty value), then replace it with a * instead:

/^[\w&.\-]*$/ 

Answer 2

Well, why not just add them to your existing character class?

var pattern = /[a-zA-Z0-9&._-]/ 

If you need to check whether a string consists of nothing but those characters you have to anchor the expression as well:

var pattern = /^[a-zA-Z0-9&._-]+$/ 

The added ^ and $ match the beginning and end of the string respectively.

Testing for letters, numbers or underscore can be done with \w which shortens your expression:

var pattern = /^[\w&.-]+$/ 

As mentioned in the comment from Nathan, if you're not using the results from .match() (it returns an array with what has been matched), it's better to use RegExp.test() which returns a simple boolean:

if (pattern.test(qry)) {     // qry is non-empty and only contains letters, numbers or special characters. } 

Update 2

In case I have misread the question, the below will check if all three separate conditions are met.

if (/[a-zA-Z]/.test(qry) && /[0-9]/.test(qry) && /[&._-]/.test(qry)) {    // qry contains at least one letter, one number and one special character }