until transducer: map_double

double_every_element.test.ts

import { double_every_element } from './double_every_element'

test('double every element', () => {

  expect(double_every_element([1, 2, 3])).toEqual([2, 4, 6])

})

double_every_element.ts

import { map } from 'ramda'

export const double_every_element =
  map(
    (number: number) => number * 2
  )