Compose functions

JavaScript

// Compose functions from right to left
const compose =
  (...fns) =>
  (x) =>
    fns.reduceRight((y, f) => f(y), x)

Examples

const lowercase = (str) => str.toLowerCase()
const capitalize = (str) => `${str.charAt(0).toUpperCase()}${str.slice(1)}`
const reverse = (str) => str.split('').reverse().join('')
const fn = compose(reverse, capitalize, lowercase)

// We will execute `lowercase`, `capitalize` and `reverse` in order
fn('Hello World') === 'dlrow olleH'