Overview

usePrevious is part of the @usefy ecosystem — a collection of production-ready, TypeScript-first, SSR-safe React hooks. It returns the previous distinct value: the value from the last render in which it actually changed (compared with Object.is by default), not simply the value one render ago. If a value is unchanged across a re-render, the returned "previous" does not advance — the behavior change-detection logic usually wants. Pass a custom comparator to treat referentially-different-but-equal values as unchanged.

Features

• Ref-based — no extra re-render to track the previous value
• Distinct tracking — a value that never changes keeps undefined
• Optional comparator — ignore new-but-equal values (defaults to Object.is)
• TypeScript-first — full type inference and exported types
• Tiny & tree-shakeable — zero dependencies, published as its own package

Installation

# npm
npm install @usefy/use-previous

# yarn
yarn add @usefy/use-previous

# pnpm
pnpm add @usefy/use-previous

Requires React 18 or 19 (peerDependencies: "react": "^18.0.0 || ^19.0.0").

Quick Start

import { usePrevious } from "@usefy/use-previous";

const [count, setCount] = useState(0);
const prev = usePrevious(count); // undefined, then the previous value

API

usePrevious<T>(value, isEqual?): T | undefined — tracks the previous distinct value; pass isEqual (defaults to Object.is) to ignore new-but-equal values.

Testing

📊 View Detailed Coverage Report (GitHub Pages) — 6 tests, 100% statement coverage.

License

MIT © mirunamu

This package is part of the usefy monorepo.