如何在Javascript中获取嵌套JSON数组的长度

Question

我有这个JSON

var data =
[
    {
        "new": [
            {
                "screen": "SCR2",
                "time_of_order": "20:08:58",
                "status": "Viewed",
                "item_id": "9,6,5,4",
                "quantity": "1",
                "vendor_id": "1",
                "order_id": "140827080458858O1O1",
                "json_value": [
                    {
                        "SurCharges": "50"
                    },
                    {
                        "SurCharges": "50"
                    },
                    {
                        "SurCharges": "50"
                    }
                ],
                "seat_number": "D12"
            }
        ]
    }
];

如何获取名为json_value的嵌套数组的长度

这是我的jsfiddle

http://jsfiddle.net/03zw041h/2/

尝试使用

警报（data.new.json_value.length）;

但是控制台报告错误

Uncaught TypeError: Cannot read property 'json_value' of undefined 

Answer 1

你有一些数组

data[0].new[0].json_value.length 

FIDDLE

Answer 2

你也有嵌套数组，所以你必须考虑到这些。

http://jsfiddle.net/03zw041h/4/

data[0].new[0].json_value.length

Answer 3

你有一个对象数组，每个对象只有一个元素，所以你可能不希望/需要它们作为数组：

var data =
{
    "new":
    {
        "screen": "SCR2",
        "time_of_order": "20:08:58",
        "status": "Viewed",
        "item_id": "9,6,5,4",
        "quantity": "1",
        "vendor_id": "1",
        "order_id": "140827080458858O1O1",
        "json_value":
        [
            {
                "SurCharges": "50"
            },
            {
                "SurCharges": "50"
            },
            {
                "SurCharges": "50"
            }
       ],
       "seat_number": "D12"
    }
};