title: How to detect a textbox's content has changed
body: <p>I want to detect whenever a textbox's content has changed. I can use the keyup method, but that will also detect keystrokes which do not generate letters, like the arrow keys. I thought of two methods of doing this using the keyup event:</p>
  
  <ol>
  <li>Check explictly if the ascii code of the pressed key is a letter\backspace\delete</li>
  <li>Use closures to remember what was the text in the textbox before the key stroke and check whether this has changed.</li>
  </ol>
  
  <p>Both look kinda cumbersome. </p>