Find previously selected combo box value in javascript

HTML form:

            Here i have taken separate hidden text  box hide the value when we first load the  page, So  then we  easily  find the  solution using the  bellow  javascript  function.

<form name="frm_country" id="frm_country" method="post">

  <select name="country1" id="country1" onchange="CountrySelected();">

     <option value="US" selected="selected">United States</option>

     <option value="UK">United Kingdom</option>

     <option value="IN">India</option>

     <option value="CH">China</option>

  </select>

  <input  type="hidden" name="country_hide" id="country_hide" value= "US">  <!-- DEFAULT US -->

</form>

         Bellow  you can the  javascript  code  to  find the  previously  selected combo box value.

  <script type="text/javascript">

       function  CountrySelected()

       {

           var pre_country_code =  document.getElementById('country_hide').value;

          //here we will  get the value      

          alert(pre_country_code);

          var cur_country_idx = document.frm_country.country1.selectedIndex;

          var cur_combo_val =   document.frm_country.country1.options[cur_country_idx].value;

          document.getElementById('country_hide').value = cur_combo_val; 

       }

  </script>