title: Checking item of array on "undefined" in JavaScript
body: <p>My JS-code has array <em>arrayResults</em>, some element of him can be "undefined" - this is feature of algorithm. To check that there is no such elements I use the follow code:</p>
  
  <pre><code>for (i in arrayResults)
          {
            if (typeof(arrayResults[i])=='undefined')
             {
                // ask user to repeat
             };
          };  
  </code></pre>
  
  <p>But, using the debugger, I found that JS-engine passes the "undefined"-item of array (in for condition), respectively I don't have the possibility to make the comparing and make the follow instructions.</p>
  
  <p>So, is there any way to really check the "undefined" items in array? (I can't to set items of array in sequence, because if I found the position of "undefined" item, I tell to user to go to this position). </p>