Functional programming concepts like immutability and pure functions offer tangible benefits for JavaScript developers, but libraries implementing them often come with a steep learning curve and niche terminology. Enter common-fp, a new open-source utility library designed to deliver FP's practical advantages without the academic baggage.

The Pragmatic FP Approach

At its core, common-fp focuses on generic data type operations – utilities that work consistently across different structures. The flagship mapValues function demonstrates this philosophy:

import { mapValues } from 'common-fp';

// Works on objects
const increment = mapValues(n => n + 1);
increment({ jason: 2, amy: 3 }); // { jason: 3, amy: 4 }

// Also works on Maps, Arrays, and Sets
const capitalize = mapValues(str => str[0].toUpperCase() + str.slice(1));
capitalize(new Set(['kim', 'grace'])); // Set { 'Kim', 'Grace' }

Unlike Lodash's per-type methods (map, mapValues, mapKeys), mapValues dynamically adapts to input types while preserving structure – returning a Map for Map input, an Array for Array input, etc. This reduces cognitive load and encourages composition.

Designed for Real-World Constraints

Creator Jason emphasizes intentional tradeoffs:

"Common FP is for people who want utilities that work generically but aren't interested in diving in the deep end. Helpful concepts like immutability can be used without knowing what an 'identity function' is."

The library explicitly targets developers who:
- Prefer readable, debuggable implementations over black-box abstractions
- Value immutable operations but dislike prototype pollution from method chaining
- Seek gradual FP adoption without rewriting entire codebases

Conscious Limitations

common-fp makes opinionated choices that define its boundaries:
1. No auto-currying: Functions don't implicitly curry arguments
2. Strict validation: Utilities throw errors for unintended usage (e.g., mapValues(null) fails)
3. No fantasy-land specs: Avoids algebraic JavaScript patterns

As the documentation notes: "If Ramda or Sanctuary makes sense to you, Common FP may feel watered down." This honesty clarifies its niche – it's a gateway drug to FP concepts, not a replacement for comprehensive FP libraries.

The Accessibility Imperative

By prioritizing approachability and debugging transparency, common-fp challenges the notion that functional programming must be academically intimidating. Its deliberately constrained scope serves as a reminder that incremental adoption of FP principles often beats rigid all-or-nothing approaches in production JavaScript environments.

Install via npm i common-fp (TypeScript types available).