title: JQuery Keyup event doesn't work
body: <p>So, I need use this event so I can navigate trought blog posts. I use the 'J' key to go to the previous post and the 'K' key to go to the next post.
  My problem is that the event works on the first try but then doesn't work anymore. 
  When i restart the browser it works if i press J or K and it redirects me to the previous/next post. But then if I press again it does nothing.</p>
  
  <p>Sorry if I can't explain it exactly enought and thanks for helping.</p>
  
  <pre><code>$(document).keyup(function (event) {
     if (event.keyCode == 74) {
        var left_link = $('#nav-left a').attr('href');
        alert(left_link);
        if(typeof left_link !== 'undefined' &amp;&amp; left_link !== false)
          window.location = left_link;
     } 
     else if (event.keyCode == 75) {
       var right_link = $('#nav-right a').attr('href');
       alert(right_link);
       if(typeof right_link !== 'undefined' &amp;&amp; right_link !== false)
         window.location = right_link;
     }
  });
  </code></pre>
  
  <p>Even if I don't do the redirect and only those alerts it doesn't work.</p>