javascript - 过滤 JSON 文件并查找值

Question

我收到一个 JSON 文件，其中包含有关多个城市的天气数据。这是数据示例。

const weatherArray = [{
            "Date": '5-1-19',
            "Location": 'New York',
            "Rainfall": 4},
                                     {
            "Date": '5-1-19',
            "Location": 'Miami',
            "Rainfall": 8},
                                     {
            "Date": '5-1-20',
            "Location": 'New York',
            "Rainfall": 9},
                                     {
            "Date": '5-1-20',
            "Location": 'Miami',
            "Rainfall": 2},
                                     {
            "Date": '5-1-21',
            "Location": 'New York',
            "Rainfall": 10},
                                     {
            "Date": '5-1-21',
            "Location": 'Chicago',
            "Rainfall": 9},
                                    ]

我需要做的是过滤这些数据并将每个城市的最大降雨量存储在一个数组中。我相信我的函数已经接近，但 filterData 返回 6 个未知对象的数组。

filterData = (inputArray) => {
    let rain = inputArray.map(obj => rain.find(o => o.Location === obj.Location && obj.Rainfall > o.Rainfall) || rain.find(o => o.Location !== obj.Location));
    return rain;
    }

我希望输出数组包含与 JSON 文件中每个城市的最大降雨量关联的整个对象。

rain = [{
        "Date": '5-1-19',
        "Location": 'Miami',
        "Rainfall": 8},
{
        "Date": '5-1-21',
        "Location": 'New York',
        "Rainfall": 10},
{
        "Date": '5-1-21',
        "Location": 'Chicago',
        "Rainfall": 9},
]

Answer 1

您可以拿一张 map ，收集某个位置的最大降雨量，并获取包含结果的新对象数组。

const
    weatherArray = [{ Date: "5-1-19", Location: "New York", Rainfall: 4 }, { Date: "5-1-19", Location: "Miami", Rainfall: 8 }, { Date: "5-1-20", Location: "New York", Rainfall: 9 }, { Date: "5-1-20", Location: "Miami", Rainfall: 2 }, { Date: "5-1-21", Location: "New York", Rainfall: 10 }, { Date: "5-1-21", Location: "Chicago", Rainfall: 9 }],
    filterData = (inputArray) => {
        return Array.from(
            inputArray.reduce((m, { Location, Rainfall }) =>
                m.set(Location, Math.max(m.get(Location) || 0, Rainfall)), new Map),
            ([Location, Rainfall]) => ({ Location, Rainfall })
        );
    };
  
console.log(filterData(weatherArray));

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带日期。

const
    weatherArray = [{ Date: "5-1-19", Location: "New York", Rainfall: 4 }, { Date: "5-1-19", Location: "Miami", Rainfall: 8 }, { Date: "5-1-20", Location: "New York", Rainfall: 9 }, { Date: "5-1-20", Location: "Miami", Rainfall: 2 }, { Date: "5-1-21", Location: "New York", Rainfall: 10 }, { Date: "5-1-21", Location: "Chicago", Rainfall: 9 }],
    filterData = (inputArray) => {
        return Array.from(inputArray
            .reduce((m, o) => {
                var temp = m.get(o.Location)
                return temp && temp.Rainfall > o.Rainfall
                    ? m
                    : m.set(o.Location, o);
            }, new Map)
            .values()
        );
    };
  
console.log(filterData(weatherArray));

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