Question

Been playing around with JavaScript, and what Im trying to do is only allow certain characters in the pass word field – a-z, A-Z and 0-9.

<form action="http://www.cknuckles.com/cgi/echo.cgi" method="get" name="logOn">
  User Name:<br />
  <input type="text" name="userName" size="25" /><br />
  Password:<br />
  <input type="password" name="pw" size="25" /><br />
  <input type="submit" value="Log In" onClick="validate()"/> 
</form>

Above is my HTML, and Below is my JavaScript I tried to use to validate it – but it doesnt work – any clues.

<script language="javascript">
   document.logOn.onsubmit=validate;

   function validate(){

var name=document.logOn.pw.value;
    if(!name = "[a-zA-Z0-9]"){              
alert("Your Password Cant Have Any Funky Things In It - Play It Straight!");
    return false;
}               

    return true;
}
</script>

But This isnt working. I can still put chars in like “*” and “[” and “{” etc.

Any Thoughts?

Answer 1

You need to make your condition test a regexp, not a string:

if(!/^[a-zA-Z0-9]+$/.test(name)){ ...

meaning:

• ^ — start of line
• [a-zA-Z0-9]+ — one or more characters/numbers
• $ — end of line

or you could search for the inverse of that, which is “any non-accepted character”:

if(/[^a-zA-Z0-9]/.test(name)){