ramda.js 如何进行groupby、count、sort

Question

我有一个这样的数据集：

[{"id":1,"score":4},{"id":2,"score":3},{"id":1,"score":4},{"id":2,"score":3},{"id":3,"score":4},{"id":1,"score":3}]

我想要这样的输出：

[{"id":1,"count":3},{"id":2,"count":2},{"id":3,"count":1}]

有什么解决方案可以使用 Ramda.js 来做到这一点吗？

我尝试使用 countBy(prop("id"))，但我不知道如何按计数排序。

Answer 1

借助 vanillaJS，您可以简单地使用 reduce 和 Map

const data = [{"id":1,"score":4},{"id":2,"score":3},{"id":1,"score":4},{"id":2,"score":3},{"id":3,"score":4},{"id":1,"score":3}]

const final = [...data.reduce((op,{id,score})=>{
   if(op.has(id)){
    op.set(id, op.get(id)+1)
   } else {
    op.set(id,1)
   }
   return op;
}, new Map()).entries()].map(([id,count])=>({id,count}))

console.log(final)

Answer 2

用R.pipe创建一个函数，用R.countBy得到一个{ [id]: count }的对象，然后将数据转换成对，用[=23]生成一个对象数组=]，和 R.applySpec。然后用R.sortBy.

排序

const { pipe, countBy, prop, toPairs, map, applySpec, head, last, sortBy, descend } = R

const fn = pipe(
  countBy(prop('id')),
  toPairs,
  map(applySpec({
    id: pipe(head, Number), // or just id: head if the id doesn't have to be a number
    count: last,
  })),
  sortBy(descend(prop('count'))), // or ascend
)

const arr = [{"id":1,"score":4},{"id":2,"score":3},{"id":1,"score":4},{"id":2,"score":3},{"id":3,"score":4},{"id":1,"score":3}]

const result = fn(arr)

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.27.0/ramda.js"></script>

Answer 3

显然 countBy 将是解决方案的一部分，如果您使用的是 Ramda。然后我会选择将其通过管道传输到 toPairs 和 zipObj 以获得最终结果：

const collect = pipe (
  countBy (prop ('id')),
  toPairs,
  map (zipObj (['id', 'count']))
) 

const data = [{id: 1, score: 4}, {id: 2, score: 3}, {id: 1, score: 4}, {id: 2, score: 3}, {id: 3, score: 4},{id: 1, score: 3}]

console .log (collect (data))

<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.27.0/ramda.js"></script>
<script> const {pipe, countBy, prop, toPairs, map, zipObj} = R             </script>

zipObj 接受一组属性个名称和一组值，并将它们压缩到一个对象中。

ramda.js 如何进行groupby、count、sort

ramda.js how to do the groupby, count, sort

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