How To Compose An Ascending/descending Sort In Ramda

I have a React component with a sorting headers table. This code works as planned: //definitions and imports... const [sort, setSort] = useState({column: 'rank', direction: 'as

Solution 1:

I think I would do something like this, wrapping ascend or descend around the composition:

const makeSorter = (sortConfig) => R.sort (
  (sortConfig.direction === 'descending' ? R.descend : R.ascend) ( R.compose (
    sortConfig.isNumber ? Number.parseFloat : R.toLower,
    R.prop (sortConfig.column)
  ))
)

const people = [
  {name: 'fred', age: 25},
  {name: 'barney', age: 28},
  {name: 'wilma', age: 29},
  {name: 'betty', age: 22}
]

const byName = {direction: 'descending', column: 'name', isNumber: false}

const getSortedData = makeSorter(byName)

console .log (
  getSortedData (people)
)

const byAge = {direction: 'ascending', column: 'age', isNumber: true}

console .log (
  makeSorter (byAge) (people)
)

<script src="//cdnjs.cloudflare.com/ajax/libs/ramda/0.26.1/ramda.js"></script>

I would personally prefer to write it with destructuring, as such:

const makeSorter = ({direction, isNumber, column}) => R.sort (
  (direction === 'descending' ? R.descend : R.ascend) ( R.compose (
    isNumber ? Number.parseFloat : R.toLower,
    R.prop (column)
  ))
)

but that doesn't change anything fundamental.

Solution 2:

You can use ascend or descend with converge:

1. The first branch works out whether that's an ascending or descending sort
2. The second branch works out which field (and which transformation) the sort should operate on

const arr = [{a: 10, b: 'ZZZ'}, {a: 5, b: 'ccc'}, {a: 11, b: 'aaa'}];

const makeSort = converge(call, [
  ({dir}) => dir === 'ascending' ? ascend : descend,
  ({isNumber, key}) => isNumber ? compose(parseFloat, prop(key)) : compose(toLower, prop(key))]);

const ascSortB = makeSort({dir: 'ascending', isNumber: false, key: 'b'});
const descSortA = makeSort({dir: 'descending', isNumber: true, key: 'a'});

console.log(sort(ascSortB, arr));
console.log(sort(descSortA, arr));

<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.26.1/ramda.min.js"></script>
<script>const {sort, ascend, descend, prop, converge, call, compose, toLower} = R;</script>

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