x/rambda/source/countBy.spec.js
12345678910111213import { countBy } from './countBy.js'const list = [ 'a', 'A', 'b', 'B', 'c', 'C' ]test('happy', () => { const result = countBy(x => x.toLowerCase(), list) expect(result).toEqual({ a : 2, b : 2, c : 2, })})