title: JavaScript KeyCode vs CharCode
body: <p>The problem:</p>
  
  <ul>
  <li>Limit allowed characters in a HTML input to a-z A-Z only.</li>
  <li>For business requirements this needs to be done on KeyPress so that the character simply isnt allowed to even appear in the input.</li>
  <li>Tab, enter, arrows, backspace, shift are all allowed. The user must be able to freely move in and out of the textbox, delete characters etc etc.</li>
  </ul>
  
  <p>This is the starting point of my code...</p>
  
  <pre><code>var keyCode = (e.keyCode ? e.keyCode : e.which);
  </code></pre>
  
  <p>However every value that I get in <em>keyCode</em> doesnt correspond to <em>any</em> of the character charts I have seen on the web. For example the character "h" gives me a return code of 104.</p>
  
  <p>Is KeyCode different to CharCode? Which code contains the control characters? Do I need to convert?</p>
  
  <p>How can I restrict the input to a-z A-Z and allow the keys I need in JavaScript?</p>