I've seen Conditionally Render HTML in Visualforce but it seems to handle the checking on the apex side then simply reference that when determining whether to display but I don't think I can do that in my case.
<script>
function myMod(num, denom){
alert(num % denom);
return (num % denom) == 0;
}
</script>
-- stuff
<apex:variable value="{!1}" var="rowNum"/>
<apex:repeat value="{!things}" var="thing">
-- stuff --
<apex:outputPanel rendered="myMod({!rowNum}, 4)" layout="none"> <hr/> </apex:outputPanel>
<apex:variable var="rowNum" value="{!rowNum + 1}"/>
</apex:repeat>
Basically the problem is that the hr/ isn't displaying