How to install prelude-ts in a Node.js TypeScript project?

Install via npm and update tsconfig.json to include es2015.iterable in the lib array for ES5 targets. Then import modules like Vector from prelude-ts using ES6 imports or require.

prelude-ts vs immutable.js: which is better for functional programming?

prelude-ts includes functional constructs like Option and Either that immutable.js lacks, but immutable.js has a larger ecosystem. Choose prelude-ts for a more integrated FP approach with immutable collections.

How to handle null safety with Option in JavaScript?

Use Option.of(value) to wrap values, then chain operations with map or flatMap to handle presence, and getOrElse for defaults, eliminating null checks and improving code safety.

What are the performance benchmarks for prelude-ts collections?

Benchmarks on the wiki show prelude-ts uses efficient algorithms like HAMT and vector tries, performing well against libraries like immutable.js, with details on runtime and memory usage.

How to use Future for async operations in prelude-ts?

Create Futures with Future.ofPromise or from callbacks, then chain with map and flatMap for transformations, providing a functional alternative to promises without async/await syntax.

prelude-ts or ramda for functional utilities?

prelude-ts offers immutable collections and a fluent API, while ramda provides global functions and currying. Pick prelude-ts for integrated data structures, ramda for standalone functional tools.

prelude.ts

ISCTypeScriptv1.0.6

A TypeScript library providing persistent immutable collections and functional programming constructs like Option, Either, and Future.

GitHub

What is prelude.ts?

prelude-ts is a TypeScript library that provides persistent immutable collections (Vector, Set, Map) and functional programming constructs like Option, Either, Predicate, and Future. It solves the problem of managing state predictably in JavaScript and TypeScript by enforcing immutability and offering functional abstractions for common programming tasks.

Target Audience

TypeScript and JavaScript developers looking to adopt functional programming patterns, especially those building applications where immutability, predictable state management, and expressive error handling are important.

Value Proposition

Developers choose prelude-ts for its focus on performance (using efficient algorithms), a fluent API that enhances code readability, and strong encouragement of structural equality—making it a practical and accessible entry into functional programming without the overhead of more complex abstractions.

Overview

Functional programming, immutable collections and FP constructs for typescript and javascript

Use Cases

Best For

Building applications with immutable state management

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Handling optional values and errors using Option and Either types

Working with persistent collections that support structural equality

Adopting functional programming patterns in TypeScript projects

Creating predictable and maintainable data transformation pipelines

Managing asynchronous operations with Future in a functional style

Not Ideal For

Projects deeply integrated with libraries that expect mutable JavaScript objects (e.g., many UI frameworks with direct state mutation)
Teams seeking a drop-in functional library without defining custom equality methods for objects
Applications where minimal bundle size is critical, as prelude-ts adds dependencies and overhead
Developers who prefer the global function style of libraries like ramda over fluent APIs

Pros & Cons

Pros

Performance-Optimized Collections

Uses efficient algorithms like HAMT for HashMap/HashSet and bit-mapped vector trie for Vector, avoiding recursion for good runtime performance, with benchmarks available on the wiki.

Fluent API Design

Prefers chainable methods like list.filter().sortBy() over global functions, enhancing code readability and intuitiveness as shown in the README examples.

Structural Equality Support

Actively encourages defining equals and hashCode for custom types, enabling proper value comparisons in collections and refusing types without these methods to prevent bugs.

Practical Functional Constructs

Provides Option, Either, Future, etc., without venturing into overly complex abstractions like monad transformers, making functional programming accessible in TypeScript.

Cons

Equality Boilerplate Required

Forces developers to implement equals and hashCode for custom types to use collections effectively, adding verbosity and complexity that can deter adoption.

TypeScript Configuration Hurdle

Requires tsconfig adjustments like adding es2015.iterable for ES5 targets, which adds setup complexity and may confuse developers new to TypeScript.

Limited Advanced FP Features

Explicitly excludes higher-level concepts like monad transformers and higher-kinded types, limiting its utility for advanced functional programming use cases.

Open Source Alternative To

prelude.ts is an open-source alternative to the following products:

i

immutable.js

Immutable.js is a JavaScript library providing persistent immutable data structures, such as Lists and Maps, for functional programming and state management.

m

monet.js

Lodash

Lodash is a popular JavaScript utility library that provides consistent, modular functions for common programming tasks like array manipulation, object iteration, and function composition.

s

sanctuary

Sanctuary is a functional programming library for JavaScript that provides safe, immutable data types and pure functions, helping developers write more reliable and maintainable code.

r

ramdajs

RamdaJS is another name for the Ramda functional programming library for JavaScript, providing utilities for functional programming patterns.