🔍 React has its own MurmurHash3 implementation… and it’s hidden in plain sight!

Inside the React source code, there's a little gem of an implementation tucked away in createFastHashJS.js. This file contain a pure JavaScript, Sync, non-cryptographic hashing function based on MurmurHash3 (32-bit).

export function createFastHashJS(key: string): number {
  return murmurhash3_32_gc(key, 0);
}

❓Why does React need this ?
React uses this fast hash internally —- for example, to hash key paths used in useActionState when handling MPA-style from submissions.
These hashes are used to track state transitions, cache component branches, or generate unique keys.

❓Why not use Web Crypto?
The browser’s crypto.subtle.digest() is asynchronous, which makes it unsuitable in React performance-critical paths where synchronous execution is essential to avoid choppy renders and high context-switching costs.

✅ MurmurHash3: The best choice
This version comes from Gary Court's highly respected JS port of the MurmurHash3 algorithm.

📦 Use Cases in environments like React.
- Component key path hashing.
- Action state deduplication.
- Deterministic memoization cache keys.
- Static asset naming (in build tools).
- ID generation in SSR contexts.

🔐 Important warning
This hash is not cryptographically secure. It’s optimized for speed and determinism, not protection. Don’t use it for passwords, tokens, or anything sensitive!

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✨ This is one of those internal utilities that reminds us: even in massive projects like React, simplicity often wins when performance is king 👑

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🔗Links
createFastHashJS.js
MurmurHash