jquery select box change event

$('select').on('change', function (e) {
    var optionSelected = $("option:selected", this);
    var valueSelected = this.value;
    ....
});
    $('#choose').change(function(event) {
        $.post('info.php', { selected: $('#choose').val() },
            function(data) {
                $('#update').html(data);
            }
        );            
    });