groupBy

Groups items by the key a function returns for each of them.

Usage

import { groupBy } from 'tsu'

const animals = [
  { name: 'Kermit', type: 'frog' },
  { name: 'Mr. Toad', type: 'toad' },
  { name: 'Slippy Toad', type: 'toad' }
]

groupBy(animals, (animal) => animal.type)
// [
//   ['frog', [{ name: 'Kermit', type: 'frog' }]],
//   ['toad', [{ name: 'Mr. Toad', type: 'toad' }, { name: 'Slippy Toad', type: 'toad' }]]
// ]

groupBy([3, 2, 4, 1, 6], (n) => n % 2 === 0)
// [[false, [3, 1]], [true, [2, 4, 6]]]

Type Definitions

/**
 * @param array - The array.
 * @param by - The function returning the key to group an item under.
 * @returns The tuple of each key and its items, in the order the keys were first seen.
 */
function groupBy<T, K>(array: readonly T[], by: (item: T) => K): [K, T[]][]