只获取对象中对象的一些关键帧

Question

我有这个对象：

const dataset = {
"2019": {
"a": 1,
"b": 2,
"c": 3,
"d": 4
},
"2020": {
"a": 2,
"b": 4,
"c": 6,
"d": 8
},
"2021": {
"a": 10,
"b": 11,
"c": 12,
"d": 13
}
}

我想获得这两个对象：

const obj1 = {
"2019": {
"a": 1,
"c": 3,
},
"2020": {
"a": 2,
"c": 6,
},
"2021": {
"a": 10,
"c": 12,
}
}
const obj2 = {
"2019": {
"b": 2,
"d": 4
},
"2020": {
"b": 4,
"d": 8
},
"2021": {
"b": 11,
"d": 13
}
}

所以"分割"；两个对象中的对象基于内部对象的一些键。以下是我尝试过的：

function pickKeys(dataObj, keys) {
return Object.entries(dataObj).map(([d, obj]) => {
return { [d]: _.pick(obj, keys) }
})
}
const obj1 = pickKeys(dataset, ['a', 'c'])

结果是：

const obj1 = [
{ '2019': { a: 1, c: 3 } },
{ '2020': { a: 2, c: 6 } },
{ '2021': { a: 10, c: 12 } }
]

差不多了，但并不完美。哪种方法更好？

Answer 1

您可以使用map、reduce方法和一个for...in循环的组合来完成此操作，该循环将把键数组转换为对象数组。然后可以使用数组析构函数来获得两个独立的对象。

const dataset = {"2019":{"a":1,"b":2,"c":3,"d":4},"2020":{"a":2,"b":4,"c":6,"d":8},"2021":{"a":10,"b":11,"c":12,"d":13}}
const [a, b] = [['a', 'c'], ['b', 'd']]
.map(keys => keys.reduce((r, key) => {
for (let year in dataset) {
if (!r[year]) r[year] = {}
r[year][key] = dataset[year][key]
}
return r;
}, {}))
console.log(a)
console.log(b)

Answer 2

问题是map返回一个带有替换元素的数组，而您需要一个对象。

由于您已经在使用Lodash，因此可以使用mapValues来转换对象的值，并返回对象而不是数组。

function pickKeys(dataObj, keys) {
return _.mapValues(dataObj, obj => _.pick(obj, keys));
}

function pickKeys(dataObj, keys) {
return _.mapValues(dataObj, obj => _.pick(obj, keys));
}
const dataset = {
"2019": {
"a": 1,
"b": 2,
"c": 3,
"d": 4
},
"2020": {
"a": 2,
"b": 4,
"c": 6,
"d": 8
},
"2021": {
"a": 10,
"b": 11,
"c": 12,
"d": 13
}
}
console.log(pickKeys(dataset, ["a", "c"]));

<script src="https://cdn.jsdelivr.net/npm/lodash@4.17.15/lodash.min.js"></script>

Answer 3

您可以使用给定对象的条目来映射所需的键。

const
dataset = { 2019: { a: 1, b: 2, c: 3, d: 4 }, 2020: { a: 2, b: 4, c: 6, d: 8 }, 2021: { a: 10, b: 11, c: 12, d: 13 } },
groups = [['a', 'c'], ['b', 'd']],
[result1, result2] = Object
.entries(dataset)
.reduce((r, [k, o]) =>
groups.map((group, i) =>
group.reduce(
(q, g) => ({ ...q, [k]: { ...q[k], [g]: o[g] } }),
r[i] || {}
)
),
[]
);
console.log(result1);
console.log(result2);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 4

下一个提供的示例代码是基于reduce的，通用但在使用中可配置。。。

function createAndCollectSubdata(collector, dataEntry) {
const { keyLists, subdataList } = collector;
const [ dataKey, dataValue ] = dataEntry;
keyLists.forEach((keyList, idx) => {
const data = subdataList[idx] || (subdataList[idx] = {});
const subdata = data[dataKey] || (data[dataKey] = {}) ;
keyList.forEach(key => subdata[key] = dataValue[key]);
});
return collector;
}
const dataset = {
"2019": {
"a": 1,
"b": 2,
"c": 3,
"d": 4
},
"2020": {
"a": 2,
"b": 4,
"c": 6,
"d": 8
},
"2021": {
"a": 10,
"b": 11,
"c": 12,
"d": 13
}
};
const [
acSubdata,
bdSubdata

] = Object.entries(dataset).reduce(createAndCollectSubdata, {
keyLists: [["a", "c"], ["b", "d"]],
subdataList: []
}).subdataList;
console.log('acSubdata :', acSubdata);
console.log('bdSubdata :', bdSubdata);

.as-console-wrapper { min-height: 100%!important; top: 0; }