title: jQuery live check if input has value
body: <p>How can I live check if an input has value using jQuery?</p>
  
  <pre><code>if ($("#reference").filter(function() { return $(this).val(); }).length &gt; 0) {
    //..
  }
  </code></pre>
  
  <p>That only checks at page load, how can I check when the user changes the value in <code>#reference</code> or leaves it blank at all?</p>