pipeAsyncFunctions.js

/**
 * pipeAsyncFunctions.js
 * tags: { JavaScript, Adapter, Function, Promise }
 * Performs left-to-right function composition for asynchronous functions.
 * Use Array.prototype.reduce() with the spread operator (...) to perform
 * left-to-right function composition using Promise.then(). The functions can
 * return a combination of: simple values, Promise's, or they can be defined as
 * async ones returning through await. All functions must be unary.
 */

const pipeAsyncFunctions = (...fns) => args =>
  fns.reduce((p, f) => p.then(f), Promise.resolve(args));

const sum = pipeAsyncFunctions(
  x => x + 1,
  x => new Promise(resolve => setTimeout(() => resolve(x + 2), 1000)),
  x => x + 3,
  async x => (await x) + 4
);

(async () => {
  console.log(await sum(5)); // 15 (after one second)
})();

pipeAsyncFunctions.js

tags: { JavaScript, Adapter, Function, Promise }
Performs left-to-right function composition for asynchronous functions.
Use Array.prototype.reduce() with the spread operator (...) to perform
left-to-right function composition using Promise.then(). The functions can
return a combination of: simple values, Promise's, or they can be defined as
async ones returning through await. All functions must be unary.