30-seconds-of-code/snippets/js/s/reverse-compose-functions.md

title, type, language, tags, cover, dateModified

title	type	language	tags	cover	dateModified
Reverse compose functions	snippet	javascript	function	rocky-beach	2020-10-22T20:23:47+03:00

Performs left-to-right function composition.

• Use Array.prototype.reduce() to perform left-to-right function composition.
• The first (leftmost) function can accept one or more arguments; the remaining functions must be unary.

const composeRight = (...fns) =>
  fns.reduce((f, g) => (...args) => g(f(...args)));

const add = (x, y) => x + y;
const square = x => x * x;
const addAndSquare = composeRight(add, square);
addAndSquare(1, 2); // 9