I know I can focus and select an HTML selectbox drop-down with jquery:
<script>
    $('#otherbox').on('change', function() {
        $("#selbox").focus();
        $("#selbox").select();
    });
</script>
But this only focuses the selectbox but it doesn't open it, I still have to click on the select-element with the mouse to open it.
How can I automatically open the selectbox by another event?
 
    