hot-memo

A lightweight memoization utility designed specifically for Bun's hot reload mode. This package helps preserve expensive computation results across hot reloads during development, significantly improving developer experience.

Why hot-memo?

When using Bun's hot reload feature (bun --hot), your application restarts whenever files change. Without memoization, expensive operations like API calls, file processing, or complex calculations are repeated on every reload, slowing down development.

hot-memo solves this by storing computation results in global memory that persists across hot reloads, using a unique salt that changes only when the process truly restarts.

Installation

bun add hot-memo

Usage

import { hotMemo } from "hot-memo";

// Expensive operation that you don't want to repeat on every hot reload
const fetchUserData = async (userId: string) => {
  console.log("Fetching user data..."); // This will only log once per process
  const response = await fetch(`/api/users/${userId}`);
  return response.json();
};

// Memoized version - result persists across hot reloads
const userData = await hotMemo(fetchUserData, ["user123"]);

How it works

• Creates a unique salt when the process starts
• Uses function signature + arguments + salt as the cache key
• Stores results in globalThis to survive hot reloads (will switch to import.meta.hot in future if it's stable enough.)
• Automatically handles async functions and returns awaited results

API

hotMemo<Args, R>(fn, args, key?)

• fn: The function to memoize
• args: Arguments to pass to the function (as readonly array)
• key: Optional custom cache key (auto-generated if not provided)

Returns a Promise that resolves to the memoized result.

Development

# Install dependencies
bun install

# Build
bun run build

# Format code
bun run fmt

License

MIT