Use the following jQuery snippet to get the value of the selected option in the select box. First create a new jQuery function
function getSelectedOption(id){
$('#' + id).val();
}
Then create your select box.
<select id="selectBox">
<option>Select</option>
<option>Red</option>
<option>Blue</option>
<option>Green</option>
<option>Yellow</option>
<option>Purple</option>
</select>
Now all you have to do to get the selected value for the select box is call the function you just created.
var text = getSelectedOption('selectBox');