JSF - execute JS after validation

Question

i have a problem with showing the right dialog!

here is a snippet of my .xhtml file:

<h:panelGroup id="global_flag_validation_failed_render">
    <h:outputText id="flag_validation_failed" value="true" 
        rendered="#{facesContext.validationFailed}"/>
</h:panelGroup>

<h:commandButton value="Cancel"
    rendered="#{!myBean.readOnly}"
    onclick="return openRightOne();"
    action="throwAway" immediate="true"
    styleClass="button">
    <f:ajax render="@form global_flag_validation_failed_render" execute="@form" onevent="openRightOne"/>
</h:commandButton>

<script  type="text/javascript">
    function openRightOne()
    {
        if(data.status === 'success'){
            if($("flag_validation_failed").length === 0){
                var a = RichFaces.$('dialog');
                return open(a);
            }else{
                var a = RichFaces.$('dialog-failed');
                return open(a);
            }
        }
    }
</script>

I want to open dialog-failed, when the validation failed and otherwise dialog.

My problem is, when I click the button non of them gets opened and the program leaves the template.

Also I don't know for sure if the JS is executed after the validation!