Posted on Sep 21 • Originally published at builder.io on Sep 21 Written by Vishwas GopinathOn September 8th, there was fresh buzz in the Javascript community: Bun v1.0, created by Jarred Sumner, had arrived. But with all the talk, many are left wondering: What's the essence of Bun? Why is everyone drawing parallels with the tried-and-true Node.js? Is Bun just another fleeting trend, or is it here to redefine the game? In this article, let’s dive deep into Bun, check out its features, and find out how it compares to the well-established Node.js.Bun is a super fast all-in-one toolkit for JavaScript and TypeScript apps. The beauty of Bun lies in its ability to streamline the development process, making it smoother and more efficient than ever. This is possible because Bun is not just a runtime, it's also a package manager, a bundler, and a test runner. Imagine having a Swiss Army knife for JS development; that's Bun for you.The inception of Node.js in 2009 was groundbreaking. However, as with many technologies, as it grew, so did its complexity. Think of it like a city. As a city expands, traffic congestion can become a problem.Bun aims to be the new infrastructure that alleviates this congestion, making things run smoother and faster. It's not about reinventing the wheel but refining it, ensuring that while we get the speed and simplicity, we don't lose the essence of what makes JavaScript unique and powerful.Bun is designed as a faster, leaner, more modern replacement for Node.js so let’s take a closer look at some comparison. But first let’s discuss one other topic.When discussing the evolution of JavaScript runtimes, it's hard to overlook Deno. Ryan Dahl, the creator of Node.js, introduced Deno as a new runtime that aimed to address some of the challenges and regrets he identified with Node.js.Deno is a secure runtime for JavaScript and TypeScript. It directly addresses many of the shortcomings of Node.js. For instance, Deno natively supports TypeScript without the need for external tools. Unlike Node.js, where scripts have broad permissions by default, Deno adopts a security-first approach requiring developers to explicitly grant permissions for potentially sensitive operations, such as file system access or network connectivity.While Deno presents a compelling alternative to Node.js, it hasn't matched Node.js's widespread adoption. Therefore, this article centers on contrasting Bun with the well-established Node.js.With Bun, we can scaffold an empty project with the command bun init -y. We have a few files generated and in index.ts, add a line, console.log("Hello, Bun!"). In the terminal, run the command bun index.ts to see “Hello, Bun!” logged.A JavaScript runtime is an environment which provides all the necessary components in order to use and run a JavaScript program.Both Node.js and Bun are runtimes. Node.js is primarily written in C++ where as Bun is written with a low-level general purpose programming language called Zig. But that is just the tip of the ice berg. Let’s take a closer look at other differences when treating Bun as a runtime alone.A JavaScript engine is a program that converts JavaScript code we write into machine code that allows a computer to perform specific tasks.While Node.js uses Google's V8 engine that power's Chrome browser, Bun uses JavaScriptCore (JSC), which is an open source JavaScript engine developed by Apple for Safari.V8 and JSC have different architectures and optimization strategies. JSC prioritizes faster start times and reduced memory usage with a slightly slower execution time. On the other hand, V8 prioritizes fast execution with more runtime optimization which may lead to more memory usage.This makes Bun fast, starting up to 4x faster than Node.js.Summary: bun ran 2.19 times faster than deno and 4.81 times faster than nodeWhile Node.js is a powerful runtime for JavaScript, it doesn't natively support TypeScript files. To execute TypeScript in a Node.js environment, external dependencies are required. One common approach is to use a build step to transpile TypeScript (TS) into JavaScript (JS) and then run the resulting JS code. Here's a basic setup that uses the ts-node package:1. Installation2. Script configurationIn your package.json, you can set up scripts to streamline the process:3. ExecutionWith the above script, you can easily run your TypeScript file:In contrast, Bun offers a more streamlined approach. It comes with a JavaScript transpiler integrated into the runtime. This allows you to directly run .js, .ts, .jsxand .tsx files. Bun's built-in transpiler seamlessly converts these files to vanilla JavaScript, facilitating immediate execution without additional steps.The difference in speed is magnified when running a TypeScript file as Node.js requires a transpilation step before it can be run.A module system allows developers to organize code into reusable segments. In JavaScript, the two primary module systems are CommonJS and ES modules (ESM). CommonJS, originating from Node.js, uses require and module.exports for synchronous module handling, ideal for server-side operations.ESM, introduced in ES6, employs import and export statements, providing a more static and asynchronous approach, optimized for browsers and modern build tools. Let's use colors for CommonJS and chalk for ESM, two popular packages for adding colored outputs to the console and to better understand the module systems.Node.js has been traditionally associated with the CommonJS module system. Here's a typical usage:For ES modules in Node.js, you have one of two options:The transition from CommonJS to ES modules (ESM) has been a complex journey. It took Node.js half a decade post ESM's introduction to support it without the experimental flag. Still, CommonJS remains prevalent in the ecosystem.Bun simplifies the module system by supporting both without any special configuration. Bun's standout feature is its ability to support both import and require() in the same file, something not natively possible in Node.js:Web APIs, integral to browser-based applications, offer tools like fetch and WebSocket for web interactions. While these have become browser standards, their support in server-side environments like Node.js has been inconsistent.In earlier versions of Node.js, Web standard APIs commonly available in browsers weren't natively supported. Developers had to rely on third-party packages like node-fetch to replicate this functionality. However, from Node.js v18, there's experimental support for the fetch API, potentially eliminating the need for these packages.Bun simplifies this by offering built-in support for these Web standard APIs. Developers can directly use stable fetch, Request, Response, WebSocket and other browser-like APIs without any additional packages. Furthermore, Bun's native implementation of these Web APIs ensures they are faster and more reliable compared to third-party alternatives.Here's an example compatible with both Node.js (v18 and above) and Bun. While it's experimental in Node.js, the same functionality is stable in Bun:Hot reloading is a feature that boosts developer productivity by automatically refreshing or reloading parts of an application in real-time as the code changes, without requiring a full restart.In the Node.js ecosystem, you have a couple of options for achieving hot reloading. One popular tool has been nodemon, which hard-restarts the entire process:Alternatively, starting from Node.js v18, there's an experimental --watch flag introduced:Both methods aim to provide real-time reloading of the application as code changes. However, they might have different behaviors, especially in certain environments or scenarios.For instance, nodemon can lead to disruptions like disconnecting HTTP and WebSocket connections, while the --watch flag, being experimental, might not offer the full suite of features and has some reported issues in the GitHub issues.Bun takes hot reloading a step further. By running Bun with the --hot flag, hot reloading is enabled:Unlike the Node.js methods that might require a full process restart, Bun reloads your code in-place without terminating the old process. This ensures that HTTP and WebSocket connections remain uninterrupted and the application state is preserved, providing a smoother development experience.When transitioning to a new runtime or environment, compatibility is often a primary concern for developers. Bun addresses this by positioning itself as a drop-in replacement for Node.js. This means that existing Node.js applications and npm packages can seamlessly integrate with Bun without any modifications. Key features that ensure this compatibility include:Bun is still evolving. It's tailored to enhance development workflows and is ideal for environments where resources are limited, such as serverless functions. The team behind Bun is striving for comprehensive Node.js compatibility and better integration with prevalent frameworksWhile Bun ensures compatibility with Node.js, it doesn't stop there. Bun ships with highly-optimized, standard-library APIs for the things you need most as a developer.Bun.file()Lazily load files and access their content in various formats. This method is up to 10x faster than its Node.js counterpart.Bun.write()A versatile API to write data to disk, from strings to Blobs. It writes up to 3x faster than Node.js.Bun.serve()Set up HTTP server or WebSocket server using Web-standard APIs. It can serve 4x more requests per second than Node.js and handle 5x more WebSocket messages than the ws package in Node.js. This backend capability is reminiscent of how developers use Express in Node.js but with the added benefits of Bun's performance optimizations.Bun also has support for sqlite and password built-in.Bun is more than just a runtime; it's an advanced toolkit that includes a powerful package manager. If you've ever found yourself patiently waiting during dependency installations, Bun offers a refreshingly faster alternative. Even if you don't use Bun as a runtime, its built-in package manager can speed up your development workflow.Check out this table comparing Bun commands with npm, Node's package manager:At a glance, Bun's commands might seem familiar but the experience is anything but ordinary. Bun boasts installation speeds that are orders of magnitude faster than npm. It achieves this by leveraging a global module cache, eliminating redundant downloads from the npm registry. Additionally, Bun employs the fastest system calls available for each operating system, ensuring optimal performance.Here's a speed comparison of installing dependencies for a starter Remix project from cache, comparing Bun and npm:The bun CLI contains a Node.js-compatible package manager designed to be a dramatically faster replacement for npm, yarn, and pnpmMoreover, a bun run