How To Only Allow Alpha Numeric Chars With JavaScript

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)){