$('input').on('keyup', function(){
        var $this = $(this);
        var $delay = 500;

        clearTimeout($this.data('timer'));

        $this.data('timer', setTimeout(function(){
                $this.removeData('timer');
                         
            $.ajax({
                type: 'POST',
                url: "/ajax/basket_ubdate.php",
                data: {id:id,quantity:quantity},
                success: function(data){
            
            }
           });
        }, $delay));

});