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$("#yourselectlistid").change(function(e) {

   console.log(this);

   if(this.value() == "whatever") {
      $('#elementid').show(); //or do all elements with class
      $('.elementsclassname').show(); //you can just alternate this to hide() if you are doing that.
   } else {
      $('#elementid').hide(); //or do all elements with class
      $('.elementsclassname').hide(); //you can just alternate this to hide() if you are doing that.
   }


})