$(document).ready(function(){
    $('#spinner, #item_price').change(function(){
        var quan = $("#spinner").attr('aria-valuenow') != "" ? parseFloat($("#spinner").attr('aria-valuenow')) : 1,
        pric = $("#item_price").val() != "" ? parseFloat($("#item_price").val()) : 0;
        $('#total_price').html(pric*quan); // show total
    });
});