javascript regex doesn't work

Question

I want to create a register form. Naturally, every user have to choose a username and a password, but I want to, that there are only small a-z characters and numbers 0-9 in the usernames. I want to use regex and javascript. Here is the code:

<!DOCTYPE HTML>  
<html lang="en-US">  
<head>  
  <meta charset="UTF-8">  
  <title></title>  
  <script type="text/javascript">  
    function check(value) {  
      valid_qwe = /[a-z0-9\-]$/;
      trying = valid_qwe.test(value);
      alert("The name: " + value + "\nBe allowed: " + trying);  
      return valid_qwe;  
    }
  </script>  
</head>  
<body>  
  <input type="text" autofocus id="qwe" name="qwe" value="" />  
  <input type="submit" onClick="check(document.getElementById('qwe').value);" value="Check" id="check" />  
</body>  
</html>

But when I'm trying to test e.g.: apple or #apple always write "true".

What should I do?

Thanks!

I think you don't want \- after number but only /[a-z0-9]$/; — Suman Bogati
– Suman Bogati, Commented Apr 19, 2014 at 14:54
Restricting the alphabet available for user names and passwords is a security failure. — Pointy
– Pointy, Commented Apr 19, 2014 at 14:57

Lugia101101 · Accepted Answer · 2014-04-19 14:51:47Z

1

Your Regexp tests if the last character is within those constraints, try using /^[a-z0-9\-]+$/.

answered Apr 19, 2014 at 14:51

Lugia101101

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Comments

raina77ow · Accepted Answer · 2014-04-19 14:58:23Z

1

Should be:

var valid_qwe = /^[a-z0-9-]+$/;

Three changes here:

the pattern itself now is one or more characters of the given range (note that + quantifier after the brackets);
it's anchored both to the end (with $) and the beginning (with ^) of the string;
no need to escape - within the character range if it's the last or the first symbol of it.

Finally, I'd rather see all the variables used within that function of yours localized - hence var.

edited Apr 19, 2014 at 14:58

answered Apr 19, 2014 at 14:51

raina77ow

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Comments

Amit Joki · Accepted Answer · 2014-04-19 14:56:30Z

0

Your regex is correct (except that you are checking the last character), but you're not matching the full string.

Add a + to your regex, which means, match one or more of the previous token.

So your regex should be:

var valid_qwe = /[a-z0-9\-]+/

answered Apr 19, 2014 at 14:56

Amit Joki

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