title: Determining whether jQuery has not found any element
body: <p>I'm using jQuery's selectors, especially id selector:</p>
  
  <pre><code>$("#elementId")...
  </code></pre>
  
  <p>How should I determine whether jQuery has found the element or not? 
  Even If the element with the specified id doesn't exist the next statement give me: <code>[object Object]</code></p>
  
  <pre><code>alert($("#idThatDoesnotexist"));
  </code></pre>