javascript - 如何在 JavaScript/Jquery 中按数组分组

Question

我有一个数组如下

array1 = [{"month":"January","location":"CENTRAL","percentage":94},
{"month":"February","location":"CENTRAL","percentage":97},
{"month":"March","location":"CENTRAL","percentage":93},
{"month":"January","location":"NORTH","percentage":95},
{"month":"February","location":"NORTH","percentage":91},
{"month":"March","location":"NORTH","percentage":98}];

我想格式化我的数组如下所示

array2= [{
    location: "CENTRAL",
    January: 94,
    February: 97,
    March: 93},
    {
    location: "NORTH",
    January: 95,
    February: 91,
    March: 98}];

我尝试按如下方式使用分组

function groupBy(list, keyGetter) {
    const map = new Map();
    list.forEach((item) => {
        const key = keyGetter(item);
        if (!map.has(key)) {
            map.set(key, [item]);
        } else {
            map.get(key).push(item);
        }
    });
    return map;
}

const grouped = groupBy(array1, arr => arr.location);
console.log(grouped);

但我没有得到相同的格式。有什么建议请问我在我的想法中缺少什么？非常感谢。

Answer 1

您确实可以使用以位置为键的 map ，但随后将普通对象作为值。您的代码中的问题是您将项目插入一个数组，而不是将月份值转换为单个对象(每个位置)的属性。

因此，给定一个包含普通对象的 map ，迭代输入并将月份属性注入(inject)那些普通对象，以及相应的百分比值，然后获取该 map 的值:

const array1 = [{"month":"January","location":"CENTRAL","percentage":94},{"month":"February","location":"CENTRAL","percentage":97},{"month":"March","location":"CENTRAL","percentage":93},{"month":"January","location":"NORTH","percentage":95},{"month":"February","location":"NORTH","percentage":91},{"month":"March","location":"NORTH","percentage":98}];

const map = new Map(array1.map(({location}) => [location, { location }]));
array1.forEach(o => map.get(o.location)[o.month] = o.percentage);
const result = [...map.values()];

console.log(result);