如何统计.json中的物体数量

Question

你如何计算这个数组 json 文件中不同对象的数量。 单个 object 是：

{
    "short_name": "Demo",
    "roi_number": 0,
    "finding": "null",
    "dt": 0.1,
    "norm_times_series": [
      [80.0, 68.16335617854995, 91.83664382145005],
      [80.0, 67.66379980989896, 92.33620019010104],
      [83.0, 72.78200156354234, 93.21799843645766],
      [83.0, 71.22165069319166, 94.77834930680834],
      [81.0, 67.74249757065954, 94.25750242934046],
      [80.0, 67.12186571458821, 92.87813428541179],
      [81.0, 68.71545011387893, 93.28454988612107]]
   }

在下面的示例中，有 4 个。

[
  {
    "short_name": "Demo",
    "roi_number": 0,
    "finding": "null",
    "dt": 0.1,
    "norm_times_series": [
      [80.0, 68.16335617854995, 91.83664382145005],
      [80.0, 67.66379980989896, 92.33620019010104],
      [83.0, 72.78200156354234, 93.21799843645766],
      [83.0, 71.22165069319166, 94.77834930680834],
      [81.0, 67.74249757065954, 94.25750242934046],
      [80.0, 67.12186571458821, 92.87813428541179],
      [81.0, 68.71545011387893, 93.28454988612107]]
   },
 {
    "short_name": "Demo",
    "roi_number": 1,
    "finding": "null",
    "dt": 0.1,
    "norm_times_series": [
      [80.0, 68.16335617854995, 91.83664382145005],
      [80.0, 67.66379980989896, 92.33620019010104],
      [83.0, 72.78200156354234, 93.21799843645766],
      [83.0, 71.22165069319166, 94.77834930680834],
      [81.0, 67.74249757065954, 94.25750242934046],
      [80.0, 67.12186571458821, 92.87813428541179],
      [81.0, 68.71545011387893, 93.28454988612107]]
   },
 {
    "short_name": "Demo",
    "roi_number": 2,
    "finding": "null",
    "dt": 0.1,
    "norm_times_series": [
      [80.0, 68.16335617854995, 91.83664382145005],
      [80.0, 67.66379980989896, 92.33620019010104],
      [83.0, 72.78200156354234, 93.21799843645766],
      [83.0, 71.22165069319166, 94.77834930680834],
      [81.0, 67.74249757065954, 94.25750242934046],
      [80.0, 67.12186571458821, 92.87813428541179],
      [81.0, 68.71545011387893, 93.28454988612107]]
   },
 {
    "short_name": "Demo",
    "roi_number": 3,
    "finding": "null",
    "dt": 0.1,
    "norm_times_series": [
      [80.0, 68.16335617854995, 91.83664382145005],
      [80.0, 67.66379980989896, 92.33620019010104],
      [83.0, 72.78200156354234, 93.21799843645766],
      [83.0, 71.22165069319166, 94.77834930680834],
      [81.0, 67.74249757065954, 94.25750242934046],
      [80.0, 67.12186571458821, 92.87813428541179],
      [81.0, 68.71545011387893, 93.28454988612107]]
   }
]

我正在做反应，我将这个 json 文件作为道具传递，所以我需要操纵道具。 我想知道 json 文件中有多少不同的条目，这样我就可以根据这个显示单选按钮的数量。

import React from 'react';

const Test = (props) => {
return (

 console.log(JSON.parse(props).length); // My attempt = prop is ouput.json

)
};
export default Test;

我的 json 文件设置为 app.js：

this.state = { apiResponse: [] };

  .then(res => res.json())
   .then(res => this.setState({ apiResponse: res }));

我这样称呼它

<Test test = {this.state.apiResponse}/>

Answer 1

将您的 JSON 数据放入JSON.parse中，然后您可以访问其上的长度属性：

JSON.parse(JSON.stringify(data)).length

Answer 2

根据您的代码，如果props.data包含您提到的示例 JSON，那么props.data.length应该已经为您提供了数组中的元素数。

如果您将道具作为字符串传递，那么只需执行

JSON.parse(props);

在访问对象的长度之前。