Anything within <% ... %> tags are parsed and
executed on the server while javascript  runs on the
client machine. Now you could go the other way around
like this.

<% Integer testVar = new Integer( 1 ); %>

<script>
var test  = <%= testVar.intValue() %>;
</script>

<% Vector myVector = new Vector();
myVector.addElements( testVar ) ; %>