title: Javascript to allow only certain characters?
body: <p>I have a text-box into which a user can input a comment. The comment could be a combination of alphabets ( lowercase or uppercase) or digits or @ or semi-colon or colon or period or comma or $ or forward slash or space or - or _. I have tried using the following function but it does not test for $ or space or - or _. How can I include these also in this JavaScript function? I also want to allow an empty string in input.</p>
  
  <pre><code>function alphanumeric(inputtxt) 
  {  
    var letters = /^[0-9a-zA-Z]+$/; 
    if(inputtxt.value.match(letters)) 
    { 
      alert('Your registration number have accepted : you can try another'); 
      document.form1.text1.focus(); 
      return true; 
    } 
    else 
    { 
      alert('Please input alphanumeric characters only'); 
      return false; 
    } 
  } 
  </code></pre>
  
  <p><strong>ANSWER</strong> is as below ( provided with the help of xdazz):</p>
  
  <pre><code>   function alphanumeric(inputtxt) 
  {  
    var letters = /^[\w\d\s@;:.,-/$/]*$/; 
    if(inputtxt.value.match(letters)) 
    { 
      alert('Your registration number have accepted : you can try another'); 
      document.form1.text1.focus(); 
      return true; 
    } 
    else 
    { 
      alert('Please input alphanumeric characters only'); 
      return false; 
    } 
  } 
  </code></pre>