Documentation

modern-fns is a collection of 145 small, focused utilities for JavaScript and TypeScript, organised into ten modules. Every function is immutable, individually importable and free of runtime dependencies.

Installation

npm install modern-fns

pnpm add modern-fns

yarn add modern-fns

Requires Node 18 or newer, or any modern browser. The package ships ESM and CommonJS builds with TypeScript declarations for both.

Import styles

All three work. Named imports are the recommended default.

// 1. Named imports — recommended. Tree-shaking removes what you do not use.
import { chunk, groupBy, diff } from 'modern-fns';

// 2. Per-function subpath — the smallest possible surface, no barrel file involved.
import chunk from 'modern-fns/array/chunk';
import diff from 'modern-fns/diff/diff';

// 3. Namespaces — handy when names would collide with your own.
import { array, object, query } from 'modern-fns';
array.chunk([1, 2, 3], 2);

CommonJS works too:

const { chunk } = require('modern-fns');

Query module naming

query.get, query.set and query.has are reachable through the namespace or the subpath (modern-fns/query/get) only. The root barrel exports the object versions of those names, so the two can never be confused.

Modules

Module	Reference
Array utilities	/array
Object utilities	/object
Object diff	/diff
String utilities	/string
Number utilities	/number
URL utilities	/url
Query string utilities	/query
Value coercion & guards	/value
Functional utilities	/functional
Collection utilities	/collection

Immutability

No exported function mutates its input. set, unset, sortBy, orderBy and every other transform return a new value, and untouched branches keep their original reference — which is what makes === change detection in Vue, React and Svelte correct and cheap.

const original = { user: { name: 'John' } };
const updated = set(original, 'user.name', 'Vishnu');

original.user.name; // 'John' — untouched
updated.user.name; // 'Vishnu'
updated === original; // false

The only stateful exceptions are documented as such: debounce, throttle, memoize and once own internal state by definition, and tap runs a callback you supply.

TypeScript

Types are generated from the implementation, so they never drift from runtime behaviour.

import { groupBy, get, pick } from 'modern-fns';

interface User {
  id: number;
  role: 'admin' | 'editor';
}

groupBy(users, 'role'); // Record<string, User[]>
groupBy(users, (u) => u.id); // Record<string, User[]>
pick(user, ['id']); // { id: number }
get<string>(user, 'company.address.city'); // string | undefined

Every selector position accepts keyof T or a function. There is no any in the public API.

Tree shaking

The package sets sideEffects: false and ships one function per file, so bundlers keep only what you import.

Import	Gzipped
import { chunk } from 'modern-fns'	0.20 kB
import { diff } from 'modern-fns'	1.35 kB
import { array } from 'modern-fns'	2.91 kB
the entire library	12.83 kB

Budgets are enforced in CI, so these numbers cannot silently regress.

Browser and runtime support

Node 18+, Chrome and Edge 90+, Firefox 90+, Safari 15+. The library targets ES2021 and uses only Intl.NumberFormat, URL, String.prototype.normalize and standard collections. There are no Node built-ins — a CI check enforces that — so the same files run in a browser, on a server and in a worker.