Transitioning from Node.js to Bun for Next.js Development

Migrating your Next.js application to leverage Bun's optimised runtime can be a strategic decision to enhance both performance and developer experience. Here's a guide to help you transition smoothly.

Overview:

What is Bun?

As the ecosystem of JavaScript evolves, developers are always looking for new tools that enhance productivity and performance. Bun is a modern JavaScript runtime designed for speed and optimisation. If you've been working with Next.js and are curious about migrating to Bun in light of Vercel's latest zero-config runtime for bun install, this article walks you through the process.

Before diving into the migration steps, it's essential to understand why Bun stands out in the crowded space of package managers:

1. Optimized Performance: Bun is not just about saving disk space; it is designed to accelerate installation processes, ensuring applications are up and running quickly.
2. Seamless Deployment with Vercel: Projects with a bun.lockb configuration can now be effortlessly deployed to Vercel. Although the Bun runtime has yet to be adopted for Serverless Functions on Vercel, its compatibility with build processes is a significant leap forward.
3. Built from Ground-Up: Developed using the Zig programming language, Bun promises a fast startup and efficient code execution. Moreover, it's designed to complement the existing JavaScript ecosystem.

Why choose Bun?

1. Swift Execution: The bun CLI is tailored to rapidly execute JavaScript/TypeScript files, package.json scripts, and executable packages. For instance, while the startup time for npm run on Linux is about 170ms, with Bun, it plummets to a mere 6ms.
2. Out-of-the-box Transpiling: Bun natively supports TypeScript and JSX. There is no need for external transpilers, as Bun transpiles's on-the-fly using its fast native mechanism.
3. Efficient Memory Utilisation: If you're working in a memory-constrained environment, Bun's --smol flag ensures reduced memory usage, albeit with a slight compromise on performance.

Making the Shift: Create the Next App

Initialisation:

Start a new Next.js project using Bun for dependency management:

bunx create-next-app        

Answer the prompts:

• Project name
• TypeScript usage
• ESLint preference
• Directory structure (either src/ or experimental app/)
• Import alias configuration

Follow the prompts to configure your project. Despite using Bun to initialise and manage dependencies, remember that running the dev server still requires Node.js due to some dependencies of Next.js on specific Node.js APIs.

Environment Variables:

Although Bun is used for initialisation and dependency management, employ Node.js for the dev server:

cd my-app
bun run dev        

You can just navigate to https://localhost:3000 to view the app. Hot-reloading is enabled by default, making development agile.

Environment Variables:

With Bun, you can directly access environment variables using Bun.env:

Bun.env.API_TOKEN;        

Set these variables in your .env file. Bun will automatically read from files like .env.local, .env.production, and .env.development based on the NODE_ENV value.

Deploying with Vercel:

Projects leveraging Bun as a package manager can be deployed to Vercel without additional configuration. Ensure you have a bun.lockb file in your project, and Vercel will automatically use bun install for dependency management.

Conclusion

The integration of Bun with Vercel is a testament to the shifting paradigms in JavaScript development. With speed, efficiency, and a seamless deployment process, developers are equipped with the tools to push the boundaries of what's possible. Please explore the official documentation provided by Vercel to get started.