title: The 'charCode' property of a keyup event should not be used. The value is meaningless
body: <p>HTML code:</p>
  
  <pre><code>&lt;input type="text" id="secrecy" name="secrecy" size="3" maxlengh="3" /&gt;Days
  </code></pre>
  
  <p>Jquery code:</p>
  
  <pre><code>$('#secrecy').keyup(function(){
  alert("ok");    
  });
  </code></pre>
  
  <p>Error message:</p>
  
  <blockquote>
    <p>The 'charCode' property of a keyup
    event should not be used. The value is
    meaningless.</p>
  </blockquote>
  
  <p>The Jquery code doesn't work.When I input something into "secrecy", an alert doesn't come out.What's wrong?</p>