Compose

A drop-in extension for Promises, adding oodles of functional goodness through composition and taking error handling to an entirely different level.

Features

• Lightweight and with almost no memory footprint, the main package export comes in at well below 1KB, unminified, ungzipped.

• A familiar Promise like interface reduces the learning curve dramatically.

• Robust types for TypeScript are included in the package by default, with specific attention in areas such as scope narrowing, for heavily nested and complex compositions.

• Interoperable with existing code by design, to ensure that it's easy to introduce incrementally to your project without any pesky migrations.

Installation

Compose is available from the NPM registry and as a GitHub Package. Whichever source you prefer to use, the installation should remain the same.

# Using NPM
npm install @emphori/compose -S

# Or, using Yarn
yarn add @emphori/compose

Examples

import { compose, reject } from '@emphori/compose'
import type { Promise } from '@emphori/promise'

// (userId: string) => Promise<Org, UserNotFound | OrgNotFound>
const getUserOrg = compose(getUser).then(getOrgForUser)

function getUser(userId: string): Promise<User, UserNotFound> {
  return User.getById(userId).then((user) => {
    return user ?? reject(UserNotFound)
  })
}

function getOrgForUser(user: User): Promise<Org, OrgNotFound> {
  return Org.getById(user.orgId).then((org) => {
    return org ?? reject(OrgNotFound)
  })
}

Contributing

If you're interested in contributing, or just want to learn more about Compose, then head over to the repository where you'll hopefully find all the information you need.

Licence

This project is released under the MIT License. Enjoy responsibly ❤️