p-compose

Like fp.compose, but for Promises.

p-compose has been designed to function like fp.compose.

This smally utility library exports a function that composes the given sync/async functions. The rightmost function can have any arity; the remaining have a fixed arity of 1.

Motivation

There's a number of modules out there for Promise function composition, but they have slight differences in expected behavior:

1. Most of them don't support unlimited arity to the rightmost function.
2. Most of them don't support non-native Promise libraries.

Usage

import compose from 'p-compose';

const fetchUserById = (id) => {
  // Make some async db call or something...
  return Promise.resolve({
    id,
    name: {
      first: 'Chuck',
      last: 'Norris',
    },
  });
};

const getUserFullNameById = compose(
  user => `${user.name.first} ${user.name.last}`,
  fetchUserById,
);

getUserFullNameById(1).then(console.log); // Prints 'Chuck Norris'

Browser Support

dist/p-compose.min.js is UMD and can be imported using require/browsers.

<script src="dist/p-compose.min.js"></script>

Note: dist/p-compose.js is the main export used by node/npm.

Using Non-Native Promises

You can use the static method using to create a new compose method that will use the provided Promise library.

import pcompose from 'p-compose';

// Creates a *new* function that will use bluebird promises.
const compose = pcompose.using(bluebird);

const doSomething = compose(a, b, ...);
const bluebirdPromise = doSomething();

Alternatives

• compose-async
• compose-p
• compose-promise