How to compare javascript variable with Jsp variable?

I want to compare a javascript variable with a jsp variable. How can I do this?

 function verify_details()
   {
    var resourceId=document.getElementById("res").value;'
    <%! String rId;%>
    <%
    for(int i=0;i<l.size();i++)
    {
      rId=l.get(i).toString开发者_Python百科();
       System.out.println("Elements Are:"+rid);
    %>
       if(resourceId==rId)
        alert("Alloted");
       else
           alert("Not Alloted");  

   <%}%>

   }

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You shouldn't be doing this in the first place. See this.

If you really want to, make a new JSP with this code in it, pass the variable you want to compare as a parameter (call that page with AJAX) and get the result.

But, that's overly complicated and this situation should really never occur in code that is well structured.

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Use some control like 'hidden' or any other. Its value will be accessible in both javascript and jsp.