dashp/src/Future.js

Utilities for monadic promises.

import {curry2, curry3} from "./internal/curry";
import nameFn from "./internal/namefn";

const of = nameFn("of", (x) => Promise.resolve(x));

const map = curry2("map", (f, p) => p.then(f));

const bimap = curry3("bimap", (left, right, p) => {
  let mark = false; // When set to true, don't run left when right throws.
  return p
    .then((x) => {
      mark = true;
      return right(x);
    })
    .catch((e) => {
      if (mark) throw e;
      return left(e);
    });
});

const ap = curry2("ap", (pf, p) => Promise.all([pf, p]).then(([f, x]) => f(x)));

const chain = curry2("chain", (f, p) => p.then(f));

export {of, map, bimap, ap, chain};
export default {of, map, bimap, ap, chain};