title: how to unselect all elements in a primefaces selectCheckboxMenu from commandbutton
body: <p>I've been trying to achieve this but no avail.</p>
  
  <p>tried :</p>
  
  <pre><code>scmWidgetVar.clear(); 
  </code></pre>
  
  <p>but no avail, is there any out of box javascript function that does this job ?</p>