Ramda Guide
Preface
How to Use This Guide
What is Ramda?
Suggested Prerequisite Knowledge
Related Projects
A Tour of Ramda
Including Ramda In A Project
Documentation, Source Code, REPL, & Cookbook
Community Resources
Where We're Going
Weathering Our First Ramda Experience
Converting Temperature Units (add, multiply, divide)
Comparing Two Temperatures (min, minBy, max, maxBy)
Keep Looking Up (Object Properties)
Our Data: The ISS' Location
Reading Shallow Object Properties (prop, propOr, props, pick, pluck)
Testing Shallow Object Properties (has, propEq, propIs, propSatisfies)
Reading Deeply Nested Object Properties (path, pathOr, paths)
Testing Deeply Nested Object Properties (hasPath, pathEq, pathSatisfies)
Unshakeable Logic
Our Data: Earthquakes
Controlling Flow (ifElse, when, unless)
Functions Instead of && and || (and, or)
Higher-Order Conditionals (both, either)
"I don't not not like your faults..." (not)
Flipping a Functions' "Truthyness" or "Falsyness" (complement)
Logic in Batches (all, allPass, anyPass)
The Functional Version of a switch (cond)
Core Ramda Ideas
"Same Input → Same Output"
Functions' Argument Order
Provide Arguments When You Feel Like It (curry)
Composing Functional Pipelines of Data (o, compose, composeWith, tap)
Grokking the Ramda Documentation's Type Signatures
Updating Objects: Speaking the Lingua Ramda
Our Data: Languages Object
Setting Key/Value Pairs On An Object (assoc, assocPath)
Omitting Keys From an Object (omit, dissoc, dissocPath)
Merging Objects (mergeRight, mergeDeepRight, mergeLeft, mergeWith)
Updating Values If They Exist (evolve)
Strings: Tying Up Loose Ends
Our Data: Footwear
Uppercasing & Lowercasing Text (toUpper, toLower)
Scanning Text for Matches (match)
Sanitizing Hashtag Text (replace, trim, test, split)
All About ['L','i','s','t','s']
Our data: Nobel Prizes
What is a List?
Taking & Dropping Items (take, takeLast, takeWhile, drop, dropLast, dropWhile)
First & Last Item Groupings (head, tail, init, last)
Searching for Items (filter, reject, find, indexOf, findIndex)
Calling a Function On Every Item (map, forEach)
Inserting, Removing, & Updating Items (insert, insertAll, remove, without, update)
Reversing, Reordering, & Sorting Items (reverse, move, sort, sortBy)
Splitting Lists (slice, splitAt, splitEvery, splitWhen)
Reducing a List to a Single Value (reduce, reduceWhile, mapAccum)
Getting Unique Items (uniq, uniqBy, uniqWith)
Testing Lists With Conditions (includes, any, all, none, startsWith, endsWith)
Combining Lists (concat, union, union, intersection, difference, symmetricDifference, symmetricDifferenceWith)
Through the Lens
Our Data: Observatories
What is a Lens? (lens, lensIndex, lensProp, lensPath)
Safe Getters for Our Data (view)
Safe Setters for Our Data (set, over)
Misc
Converting an Existing API Into a Functional One (invoker)
Understanding Ramda Further by Recreating Parts of It
Using Ramda With TypeScript
Opinionated Best Practices
The Rule of 3
Type, Param, or Pseudo-Type Declarations
Writing Declarative Code That Tells a Story
You Might Not Need Ramda
Your Next Steps
Introducing FP at Work
How to Guide Others
The Larger FP World

How to Use This Guide

The Content

This guide's content consists of chapters grouped into related sections. Each section has a theme that is based on the data we use as examples.

Here are some example data we'll work with:

Weather
The International Space Station's location
Earthquakes
Internationalization (i18n)
Observatories

Many examples include explanations outside and inside code blocks; the latter are done via code comments.

Advanced Content

Content that I deemed to be advanced and perhaps not immediately relevant for newcomers is marked as "Advanced" in chapters where the advanced material is contained.

Meta

This guide is generated via mdBook. Here are some quick tips:

Open & close the sidebar by mashing on the three horizontal lines (hamburger) icon above
Change the theme by mashing on the paint brush icon above
Do a text search through the entire guide by mashing on the magnifying glass icon above
Not a fan of reading on the web? Mash the printer icon above and print it or save to PDF
Want to link to a specific heading? Each heading is a link you can mash, and then you can share the URL with the world

Disclaimer / Personal Note

Even though I've worked with Ramda since 2016, programmed professionally since 2011, and taught programming for a while, I don't have a computer science degree (yet), and I am not a Category Theory expert. The opinions in this guide stem from my experience learning functional programming concepts through a number of languages and making heaps of mistakes along the way. There are also a lot of people who invested in me, and I am thankful for their guidance along the path.

If you find mistakes or hold different opinions, feel free to open an issue, and we can publicly discuss things there.

I'll never stop learning and being better than I was yesterday, and I hope that perspective provides you, dear reader, some value as you embark on your functional programming journey.