I have two datepickers and one combobox in HTML. The combobox contain 2 values (6 months and 1 year). If I select 6 months from the combobox the second datepicker should show the date after 6 months from the first datepickers date.

I need code for this using JavaScript only not in jQuery.

My code is

```
<html>
  <body>
    <select>
      <option value="6">6 Months</option>
      <option value="12">1 Year</option>
    </select>
    <input type="date" name="Sdate" id="Sdate">
    <input type="date" name="edate" id="edate">
  </body>
</html>

```