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

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