Pass new value when calling onchange or ajaxReRender on select2 widget

<a4j:region>
         <a4j:jsFunction name="#{widget.id}_reRender"
           reRender="#{widget.id}_nestedLayout">
           <a4j:actionparam name="param1" assignTo="#{widgetProperty_valueListener}"/>
         </a4j:jsFunction>
     </a4j:region>