Question about val() method on drop down select

Question about val() method on drop down select

Please refer to  https://jsfiddle.net/edby27mL/4/


HTML
<select multiple>
  <option value="volvo">Volvo</option>
  <option value="saab">Saab</option>
  <option value="mercedes">Mercedes</option>
  <option value="audi">Audi</option>
</select>
<div></div>

JS
$('select').change(
function(event)
  {
  //selArray=$('select').val() || [] works
    // this doesnt
  selArray=$('select option:selected').val() || [];
    $('div').text(selArray.join(', '));
  }
);

Here $('select option:selected').val() doesn't work but $('select').val() works. Why?