Getting value of select (dropdown) before change

Answer 1

keep the currently selected drop down value with chosen jquery in a global variable before writing the drop down 'on change' action function. If you want to set previous value in the function you can use the global variable.

//global variable
var previousValue=$("#dropDownList").val();
$("#dropDownList").change(function () {
BootstrapDialog.confirm(' Are you sure you want to continue?',
  function (result) {
  if (result) {
     return true;
  } else {
      $("#dropDownList").val(previousValue).trigger('chosen:updated');  
     return false;
         }
  });
});