function change_cart(itemid,action){
	$.get('change_cart.php?action='+action+'&item='+itemid+'&r='+Math.random(),function(data){
		if(data == 'ok'){
			var num = $('#item_'+itemid).val();
			var total_price = parseFloat($('#total_price').html());
			var item_price = parseFloat($('#price_'+itemid).html());
			if(action == 'decrease'){
				if(num > 0){
					num--;
					total_price -= item_price;
					total_price = total_price.toFixed(2);
					$('#total_price').html(total_price);
				}
			}
			else{
				num++;
				total_price += item_price;
				total_price = total_price.toFixed(2);
				$('#total_price').html(total_price);
			}
			$('#item_'+itemid).val(num);
		}
	});
}
function update_cart(num,itemid){
	$.get('change_cart.php?action=update&item='+itemid+'&num='+num+'&r='+Math.random(),function(data){
		if(data != 'error'){
			var old_num = parseInt(data);
			var current_num = parseInt(num);
			var total_price = parseFloat($('#total_price').html());
			var item_price = parseFloat($('#price_'+itemid).html());
			
			total_price = total_price - (old_num - current_num)*item_price;
			total_price = total_price.toFixed(2);
			$('#total_price').html(total_price);
			
		}
		else{
			alert('数量输入有误,请重新输入!');
		}
	});
}
function cart_del(itemid){
	if(confirm('确定删除该商品?')){
		$.get('change_cart.php?action=del&item='+itemid+'&r='+Math.random(),function(data){
			if(data != 'error'){
				var old_num = parseInt(data);
				var total_price = parseFloat($('#total_price').html());
				var item_price = parseFloat($('#price_'+itemid).html());
				
				total_price = total_price - old_num*item_price;
				total_price = total_price.toFixed(2);
				$('#total_price').html(total_price);
				
				$('#cart_'+itemid).remove();
				
			}
			else{
				alert('暂时无法处理您的请求,请稍后再试!');
			}
		});
	}
}
function cart_empty(){
	if(confirm('确定清空购物车?')){
		$.get('change_cart.php?action=empty&r='+Math.random(),function(data){
			$('#cart_lists').remove();	
			$('#cart_empty').show();
			$('#cart_action').remove();	
		});
	}
}