ramda

What is ramda?

Ramda is a functional programming library for JavaScript that makes it easy to create functional pipelines, without mutating data. It emphasizes a purer functional style, with functions that are automatically curried and composed of small, reusable, and combinable functions.

What are ramda's main functionalities?

Immutability and Side-Effect Free Functions

Ramda functions do not mutate the input data and do not cause side effects, making it easier to reason about code.

const increment = R.map(R.add(1));
const result = increment([1, 2, 3]); // [2, 3, 4]

Function Composition

Ramda provides compose and pipe functions for combining functions into new functions, facilitating functional composition.

const getNames = R.compose(R.map(R.prop('name')), R.filter(R.propEq('isActive', true)));
const users = [{name: 'Alice', isActive: true}, {name: 'Bob', isActive: false}];
const activeUserNames = getNames(users); // ['Alice']

Automatic Currying

Ramda functions are automatically curried, allowing you to easily create new functions by partially applying arguments.

const addFourNumbers = (a, b, c, d) => a + b + c + d;
const curriedAddFourNumbers = R.curry(addFourNumbers);
const f = curriedAddFourNumbers(1, 2);
const g = f(3);
const result = g(4); // 10

Data Transformation

Ramda provides a suite of tools for transforming data structures, such as arrays and objects, in a declarative and functional way.

const sortByAge = R.sortBy(R.prop('age'));
const people = [{name: 'John', age: 23}, {name: 'Jane', age: 21}];
const sortedPeople = sortByAge(people); // [{name: 'Jane', age: 21}, {name: 'John', age: 23}]

Other packages similar to ramda

lodash

Lodash is a JavaScript utility library that offers similar functionality to Ramda, such as data manipulation and functional utilities. However, Lodash is not as strictly functional as Ramda and does not emphasize currying and function composition to the same extent.

underscore

Underscore.js is another utility library that provides functional programming helpers. It is similar to Lodash and predates both Lodash and Ramda. It has a more OOP-style approach and lacks the auto-currying and functional composition features that are core to Ramda.

immutable

Immutable.js provides persistent immutable data structures which can be used in a functional programming style. Unlike Ramda, which works with plain JavaScript types, Immutable.js uses its own types and provides different APIs for manipulating these structures.

fp-ts

fp-ts is a library for typed functional programming in TypeScript. It provides type-safe functional programming structures and utilities, and it is more focused on types and type-level programming compared to Ramda.