compose

78 bytes

Usage

In a composition of functions, each function is given the next function as an argument and must call it to continue executing.

import * as _ from 'radashi'

const useZero = (fn: any) => () => fn(0)
const objectize = (fn: any) => (num: any) => fn({ num })
const increment =
  (fn: any) =>
  ({ num }: any) =>
    fn({ num: num + 1 })
const returnArg = (arg: any) => (args: any) => args[arg]

const composed = _.compose(
  useZero,
  objectize,
  increment,
  increment,
  returnArg('num'),
)

composed() // => 2

This can be a little jarring if you haven’t seen it before. Here’s a broken down composition. It’s equivalent to the code above.

const decomposed = useZero(objectize(increment(increment(_.returnArg('num')))))

decomposed() // => 2