如何使用JSON.parse查找JSON的长度? [英] How to find length of JSON using JSON.parse?

问题描述

我有一个像这样的杰森 {"0":{"parent_id":1649,"id":"1803","last_update_on":"2010-12-24 07:01:49","message":"dhb;lxd","created_by_id":"21","created_by_name":"Amol Deshpande"}}. 因此，理想情况下，考虑到我在第0个位置上只有1个值，我应该将长度设为1.

I have a Json like this {"0":{"parent_id":1649,"id":"1803","last_update_on":"2010-12-24 07:01:49","message":"dhb;lxd","created_by_id":"21","created_by_name":"Amol Deshpande"}}. So ideally i should get length as 1 considering i have only 1 value on 0th location.

如果我有这样的JSON

what if i have a JSON like this

{"0":{"parent_id":1649,"id":"1803","last_update_on":"2010-12-24 07:01:49","message":"dhb;lxd","created_by_id":"21","created_by_name":"Amol Deshpande"},"1":{"parent_id":1649,"id":"1804","last_update_on":"2010-12-24 07:02:49","message":"amol","created_by_id":"21","created_by_name":"Amol Deshpande"}}

如果我发出警报(response.length)，我将获得未定义的值；如上所述，响应是我的JSON

I am getting the value as undefined if i do alert(response.length); where response is my JSON as mentioned above

有什么建议吗?

推荐答案

对象没有.length属性...不是您正在考虑的方式(它是undefined)，而是 Arrays 要获得长度，您需要对键进行计数，例如:

Objects don't have a .length property...not in the way you're thinking (it's undefined), it's Arrays that have that, to get a length, you need to count the keys, for example:

var length = 0;
for(var k in obj) if(obj.hasOwnProperty(k)) length++;

或者，或者使用 keys集合在大多数浏览器上可用:

Or, alternatively, use the keys collection available on most browsers:

var length = obj.keys.length;

MDC为不提供"t 已经有.keys :

Object.keys = Object.keys || function(o) {
    var result = [];
    for(var name in o) {
        if (o.hasOwnProperty(name))
          result.push(name);
    }
    return result;
};

或者，选择#3，实际上使JSON成为数组，因为这些键似乎意义不大，如下所示:

Or, option #3, actually make your JSON an array, since those keys don't seem to mean much, like this:

[{"parent_id":1649,"id":"1803","last_update_on":"2010-12-24 07:01:49","message":"dhb;lxd","created_by_id":"21","created_by_name":"Amol Deshpande"},{"parent_id":1649,"id":"1804","last_update_on":"2010-12-24 07:02:49","message":"amol","created_by_id":"21","created_by_name":"Amol Deshpande"}]

然后，您可以根据需要使用.length，并且仍然可以通过索引访问成员.

Then you can use .length like you want, and still access the members by index.

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