Lodash:如何找到每个id的最大值和最小值

Question

我的数据数组是

array = [{id: 2, name: "kent", status_id: 2, date_1: "2018-08-09", date_2: "2018-07-06"},{id: 2, name: "kent", status_id: 10, date_1: "2018-01-09", date_2: "2018-09-06"},{id: 3, name: "tracy", status_id: 2, date_1: "2018-05-03", date_2: "2018-10-02"},{id: 3, name: "tracy", status_id: 2, date_1: "2018-01-10", date_2: "2018-09-12"},{id: 3, name: "tracy", status_id: 10, date_1: "2018-02-10", date_2: "2018-09-02"},{id: 4, name: "lucy", status_id: 10, date_1: "2018-12-10", date_2: "2018-08-09"},{id: 5, name: "steve", status_id: 10, date_1: "2018-12-7", date_2: "2018-04-01"}]

如果id＝2，我想找到max(date_1(&min(date_2(。就像我的输出一样，

id
2    max(date_1)   min(date_2)
3    max(date_1)   min(date_2)
4    max(date_1)   min(date_2)
5    max(date_1)   min(date_2)

我正在使用Lodash库。我将感谢你的帮助。

Answer 1

您可以首先使用groupByid，然后使用mapValues映射每个分组值，因为这将是一个对象。映射分组值时，可以使用_.maxBy和_minBy来查找最大值和最小值

var array = [{"id":2,"name":"kent","status_id":2,"date_1":"2018-08-09","date_2":"2018-07-06"},{"id":2,"name":"kent","status_id":10,"date_1":"2018-01-09","date_2":"2018-09-06"},{"id":3,"name":"tracy","status_id":2,"date_1":"2018-05-03","date_2":"2018-10-02"},{"id":3,"name":"tracy","status_id":2,"date_1":"2018-01-10","date_2":"2018-09-12"},{"id":3,"name":"tracy","status_id":10,"date_1":"2018-02-10","date_2":"2018-09-02"},{"id":4,"name":"lucy","status_id":10,"date_1":"2018-12-10","date_2":"2018-08-09"},{"id":5,"name":"steve","status_id":10,"date_1":"2018-12-7","date_2":"2018-04-01"}]
var res = 
_(array)
.groupBy('id')
.mapValues(a => ({
max: _.maxBy(a, 'date_1').date_1,
min: _.minBy(a, 'date_2').date_2
})).value();

console.log(res);

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