title: jQuery: Make a Button Visible When a TextBox Has Contents
body: <p>Given: I have a textbox and a hidden button.</p>
  
  <p>Wanted: When the textbox is neither null nor empty, show the button. When the textbox is null or empty, hide the button.</p>
  
  <p>Question: How should I do this? Should I use jQuery and bind to the textbox's keyup event?</p>