Using f:param + f:ajax onvent results in an error

<h:form prependId="false">
    <h:commandLink action="#{sampleBean.doAction}">
        <h:outputText value="Click Me!"/>
        <f:param name="var1" value="NEW VALUE"/>
        <f:ajax event="click"
                execute="@this"
                onevent="testJs">
        </f:ajax>
    </h:commandLink>
</h:form>

<script>
    //<![CDATA[
    function testJs(data) {
        if (data.status === 'success') {
            alert("Success click")
        }
    }
    //]]>
</script>

jsf.util.chain(this, event,function(event){myfaces.ab(this,event,'click','j_id_i','',{'onevent':testJs,'var1':'NEW VALUE'})}); return false;

jsf.util.chain(this, event,function(event){myfaces.ab(this,event,'click','j_id_i','',{'onevent':testJsparams:{'var1':'NEW VALUE'}})}); return false;