javascript - Ramda 在 javascript 中的数组

Question

  var censusMembers = Object.freeze([
    {
    id: 1,
    name: 'Bob'
    }, {
    id: 2,
    name: 'Sue'
    }, {
    id: 3,
    name: 'Mary',
    household_id: 2
    }, {
    id: 4,
    name: 'Elizabeth',
    household_id: 6
    }, {
    id: 5,
    name: 'Tom'
    }, {
    id: 6,
    name: 'Jill'
    }, {
    id: 7,
    name: 'John',
    household_id: 6
    }
    ]);

这是我的数组我想使用 ramda 函数计算具有家庭 ID 的元素的数量？我该怎么做？

Answer 1

您还可以使用 R.countBy使用 R.has() 计算所有具有/不具有 household_id 的项目，然后使用 R.prop() 获取 true 的计数:

const { pipe, countBy, has, prop } = R;

const censusMembers = Object.freeze([{"id":1,"name":"Bob"},{"id":2,"name":"Sue"},{"id":3,"name":"Mary","household_id":2},{"id":4,"name":"Elizabeth","household_id":6},{"id":5,"name":"Tom"},{"id":6,"name":"Jill"},{"id":7,"name":"John","household_id":6}]);

const countHouseholders = pipe(
  countBy(has('household_id')),
  prop('true'),
);

const result = countHouseholders(censusMembers);

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.25.0/ramda.js"></script>