I have got a requirement to add asynchronous javascript to ADF pages and started using af:resource component but there is no option to add custom attribute for af:resource component. But here is the way..
Page content:
<af:document id="d1">
<af:form id="f1"></af:form>
<af:clientListener method="sayHello" type="load"/>
<f:facet name="metaContainer">
<f:verbatim>
<![CDATA[
<script src="../scripts/tester.js" async></script>
]]>
</f:verbatim>
</f:facet>
</af:document>
Application structure