multiple select
HTML
<select multiple id="myselect">
<option value="New York">New York</option>
<option value="Londres">Londres</option>
<option value="Berlin">Berlin</option>
<option value="Zurich">Zurich</option>
</select>
JavaScript
$(document).ready(function(){
$('#myselect').on('change', function(){
window.console.log($(this).val());
})
})