jquery option operate

http://www.electrictoolbox.com/jquery-add-option-select-jquery/

How to Remove All Options from a Dropdown Select Box with JavaScript

To remove all options from a dropdown select box with JavaScript, simply set the length property of the dropdown box to 0. For instance, if a dropdown select box is defined as follows:

<select name='Dropdown' id='Dropdown'>
  <option value='1'>1</option>
  <option value='2'>2</option>
</select>

Use this JavaScript to remove all the options in the dropdown select box.

document.getElementById('Dropdown').length = 0;