javascript - 在 JavaScript 中解析 JSON 对象数组

Question

我有一个 JSON 字符串:

{
    "country": "Mauritius",
    "provinces": [
        "mainland"
    ],
    "timeline": {
        "cases": {
            "3/19/20": 3,
            "3/20/20": 12,
            "3/21/20": 14,
            "3/22/20": 28,
            [...]
            "4/17/20": 324
        },
        "deaths": {
            "3/19/20": 0,
            "3/20/20": 0,
            "3/21/20": 1,
            "3/22/20": 2,
            [...]
            "4/17/20": 9
        },
        "recovered": {
            "3/19/20": 0,
            "3/20/20": 0,
            "3/21/20": 0,
            "3/22/20": 0,
            [...]
            "4/17/20": 108
        }
    }
}

我想要实现的是将病例、死亡和恢复的值解析为 JavaScript 中的单独数组。

例如，病例数，我想查找与前一个日期的病例数差异，起始日期为 3/19/20，初始病例数为 3。我想对死亡和康复应用相同的逻辑。因此，3/20/20 的值为 9 (12 - 3)

最后，我想将每个数据存储在数组中，以便在图表上使用这些数据。有人可以帮我用 JavaScript 或 JQuery 解析这些数据吗？

$.getJSON('https://corona.lmao.ninja/v2/historical/mauritius?lastdays=30', function(data) {

  let result = data.map(function(e) {
    return {
      cases: e.timeline.cases,
      deaths: e.timeline.deaths,
      recovered: e.timeline.recovered
    };
  }).reduce(function(acc, e) {

    Object.keys(e).forEach(function(t) {
      Object.keys(e[t]).forEach(function(d) {
        acc[t][d] = (acc[t][d] || 0) - e[t][d];
      });
    });
    return acc;
  }, {
    deaths: {},
    recovered: {},
    cases: {}
  });
  console.log(result)
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

Answer 1

以下使用 Array#reduce将从服务器返回的绝对值转换为天数之间的差异。

const entries = Object.entries, log = console.log, toJSON = JSON.stringify

const Δ = (arr, prev = 0) => 
  arr.reduce((acc, [date, curr]) => 
    (acc[date] = curr - prev, prev = curr, acc), {})
  
const AUTHORITY = 'corona.lmao.ninja'
async function fetchDeltas({ country, days = 30 }) {  
  const url = `//${AUTHORITY}/v2/historical/${country}?lastdays=${days}`
  const { timeline: { cases, deaths, recovered } } = await (await fetch(url)).json()
  return { 
    newCases: Δ(entries(cases)), 
    newDeaths: Δ(entries(deaths)),
    newRecoveries: Δ(entries(recovered))
  }
}
fetchDeltas({ country: 'mauritius' }).then(log)