title: Finding all checkboxes are checked in jQuery
body: <p>I have a collection of checkboxes</p>
  
  <pre><code> &lt;input id="1" class="paid" type="checkbox" /&gt;
   &lt;input id="2" class="paid" type="checkbox" /&gt;
   &lt;input id="3" class="paid" type="checkbox" /&gt;
   &lt;input id="4" class="paid" type="checkbox" /&gt;
  </code></pre>
  
  <p>I would like to write some jQuery to check if all checkboxes are checked then perform an action but how?</p>