// sync true/false - run script in sync mode.
// ..........
ajaxFunction.addParameter(buildEventOptions(facesContext, uiComponent));
// appendAjaxSubmitParameters(facesContext, uiComponent, onEvent);
ajaxFunction.appendScript(onEvent);
if (uiComponent instanceof AjaxSupport) {
AjaxSupport support = (AjaxSupport) uiComponent;
if (support.isDisableDefault()) {
onEvent.append("; return false;");
}