Logging edits to a record

Dan, may you check the code:
(function(){
  var querystring=document.location.search;

  if(/a=er/i.test(querystring)) {

$("#_fid_797").attr("readonly", "readonly");

var label, oldValue, newValue, log;

$("#_fid_242,#_fid_138").on("change", function() {

  log = [];
  _.each([242,138], function(fid) {
    oldValue = $("[name=_fid_oval_" + fid + "]").val();
    newValue = $("#_fid_" + fid).val();
    if (oldValue != newValue) {
      label = $("label[for=_fid_" + fid + "]").text();
      log.push(label + " was =" + oldValue + "; now =" + newValue);
    }
  });
  $("#_fid_797").html(log.join("\n"));
      });
    }
})();


Thank you!