folktale

What is folktale?

Folktale is a standard library for functional programming in JavaScript. It provides a set of tools to help developers write more predictable and maintainable code by using functional programming patterns.

What are folktale's main functionalities?

Data.Task

Data.Task is used for handling asynchronous operations in a functional way. It allows you to compose tasks and handle success and failure cases explicitly.

const { task } = require('folktale/concurrency/task');

const readFile = (filename) => task(resolver => {
  require('fs').readFile(filename, 'utf8', (err, data) => {
    if (err) resolver.reject(err);
    else resolver.resolve(data);
  });
});

readFile('example.txt').run().listen({
  onRejected: (error) => console.error('Error:', error),
  onResolved: (data) => console.log('File content:', data)
});

Data.Maybe

Data.Maybe is used to represent optional values. It helps in avoiding null or undefined values by providing a way to handle the presence or absence of a value explicitly.

const { Just, Nothing } = require('folktale/maybe');

const findUser = (username) => {
  const users = { alice: 'Alice', bob: 'Bob' };
  return users[username] ? Just(users[username]) : Nothing();
};

const user = findUser('alice');
user.matchWith({
  Just: ({ value }) => console.log('User found:', value),
  Nothing: () => console.log('User not found')
});

Data.Either

Data.Either is used for computations that can fail. It represents a value that can be either a success (Right) or a failure (Left), allowing you to handle both cases explicitly.

const { Left, Right } = require('folktale/either');

const parseJSON = (jsonString) => {
  try {
    return Right(JSON.parse(jsonString));
  } catch (e) {
    return Left(e.message);
  }
};

const result = parseJSON('{ "name": "Alice" }');
result.matchWith({
  Right: ({ value }) => console.log('Parsed JSON:', value),
  Left: ({ value }) => console.log('Error:', value)
});

Other packages similar to folktale

ramda

Ramda is a practical functional library for JavaScript programmers. It focuses on immutability and side-effect-free functions, similar to Folktale. However, Ramda is more focused on providing utility functions for data transformation and manipulation, whereas Folktale provides a more comprehensive set of tools for functional programming patterns.

lodash-fp

Lodash-fp is a version of Lodash with its methods wrapped to produce immutable, auto-curried, iteratee-first, and data-last methods. It offers functional programming utilities similar to Folktale, but it is more focused on providing a functional interface to Lodash's utility functions rather than a complete functional programming toolkit.

monet

Monet is a library that provides a set of functional programming constructs such as Maybe, Either, and IO. It is similar to Folktale in that it offers algebraic data types and functional patterns. However, Monet is more focused on providing a set of monadic structures, while Folktale offers a broader range of functional programming tools.

README

Folktale

Folktale is a standard library for functional programming in JavaScript.

Installing

Folktale can be installed through npm:

$ npm install folktale

Not using Node.js? Check out our guide to running Folktale in other environments!

Documentation

• Browse the HTML documentation for Folktale

If you find any functionality that's not documented, or whose documentation is confusing or hard to understand, please report a bug on our issue tracker

Supported platforms

Folktale is written for ECMAScript 2015 platforms, but it uses a subset of features that can be safely backported to platforms as old as ECMAScript 3. If you're running your program in an older platform, you'll need es5-shim and es6-shim.

• Node 4.x, Node 6+ (Node 5.x is not supported)

Browsers:

• Chrome 36+
• Firefox 21+
• Safari 6+
• Internet Explorer 9+
• Edge 13+
• Opera 12.12+

Mobile browsers:

• Android 4.4+
• iOS 8.3+

Support

Note that all interactions in this project are subject to Origami Tower's Code of Conduct.

Having trouble using Folktale?

• "I think I found a bug in Folktale"
• "There's no documentation for X" / "The docs are hard to understand"
• See the Frequently Asked Questions for common issues
• Join the discussion channel

Think Folktale should do something it doesn't yet?

• I want to propose a new feature
• I want to submit a patch/pull request

By submitting a Pull Request you agree with releasing your code under the MIT licence.

Folktale discussion channels and information

• Discussion channel @ Gitter
• Follow @origamitower for news on Folktale
• Email the organisation directly

Licence

Folktale is copyright (c) Quildreen Motta 2015-2017, and released under the MIT licence. See the LICENCE file in this repository for detailed information.