🤓 Functional Programming Workshop

⚠️ WARNING: ⚠️ Please do not look at the /solutions directory before attempting the recipes yourself. The forest comes before the machete.

💾 Installation

1. Download repo

git clone git@github.com:manuscriptmastr/fp-workshop.git
cd fp-workshop

2. Install Node 14 (this package uses modules)

nvm install 14
nvm use 14

3. Install package dependencies

npm install

⌨️ Scripts

# Run test suite
npm run test

# Run only contents of playground.js
npm run playground

🧪 Experiment

playground.js is just a blank "notepad" for you can follow along the workshop or jot down ideas/experiments. You can execute it with npm run playground.

🏃 Practice

To practice a recipe, navigate to {recipe}/index.test.js and replace the line import {recipe} from '../solutions/{recipe}' with import {recipe} from '.' Run npm run test and tests should fail. Define your recipe in {recipe}/index.js until all tests pass!

If you get stumped, you can always refer to solutions/{recipe}.js. But who does that help 🤷‍♂️?

ℹ️ Library Documentation

• Ramda is an auto-curried utility library
• Sanctuary is another FP utility library (stricter than Ramda) that includes containers like Maybe and Either
• Assert is a super chill testing library built into Node.js
• AVA is a highly explicit and concurrent testing framework
• Nock is a sweet library for mocking highly specific HTTP responses

❓ FAQ

• What's with comments like add :: Number -> Number -> Number?
  • This is a style of writing type signatures widely adopted in the functional programming community. Don't worry if it looks bizarre now — we'll see this syntax many, many times!
• An example or test is incorrect.
  • Submit an issue so we can keep this workbook up to date for posterity!
• How do I slowly build my containers without having all these failing tests?
  • In ava.config.js, uncomment all but the container method(s) you're testing. For instance, if you're trying to make Identity pass the Functor tests, you will leave only !*.map* commented out. Restart npm run test and it will pick up only tests that call SomeContainer.map(...).

😍 More FP please!

• Books
  • Professor Frisby's Mostly Adequate Guide to Functional Programming covers a generous amount of FP theory, like containers, category theory, and natural transformations
  • JavaScript Allongé is basically the dictionary of functional recipes
• Libraries
  • Fantasy Land is the official JS spec for FP libraries. Fun fact: the name of the spec was coined during a GitHub debate on whether Promises should follow the definition of a Monad (such as the Task container). Because the final Promise spec was a compromise between category theory and imperative flow, Promises cannot be cancelled unlike a Task.
  • Fluture is a Fantasy Land compliant implementation of the Task or Future container.
  • Haxl is an open source Haskell library that Facebook uses to process some 1 million post requests for spam... per second. To simplify spam definitions, the team took advantage of FP's natural cacheability and parallelism to hide concurrency logic from the developer writing a spam rule. They wrote a paper on the container type that inspired this framework.
• Talks
  • Hey Underscore, You're Doing it Wrong! shows off how currying and composition can drastically reduce boilerplate (and bugs) while increasing reusability
  • 2016 React Rally — "Oh Composable World!" experiments with FP and ReactJS
  • Classroom Coding with Professor Frisby is an almost adorable video series based on Mostly Adequate Guide
  • JavaScript and Our Obsession with Speed offers insights on the JS performance vs. maintainability discussion around declarative code
  • A Million Ways to Fold in JS explores looping alternatives via recursion, reduction, folding, and catamorphisms