What is Bun? A Fast Runtime Node.js Alternative
The JavaScript ecosystem is dynamic and ever-evolving. JavaScript Developers nowadays must make informed decisions not only of the libraries but of JavaScript runtime as well. Choosing the right runtime can have profound effects on the performance and maintainability of an app, and possibly even more on the development experience.
Bun is the new kid on the block in the world of JavaScript runtimes. Its 1.0 announcement – full of powerful features – understandably created a lot of buzz in the ecosystem. In this article, we’ll go over what Bun is, what it offers, and how it compares with the de facto standard non-browser runtime, Node.js. By the end, you’ll be able to make an informed decision on a runtime for your new or existing project.
Table Of Contents
JavaScript Engines and Runtimes
Before we begin it’s important to understand what a JavaScript engine and a runtime are, as well as how they’re different.
A JavaScript engine is a program that ingests valid JavaScript code and executes it. JavaScript is not exactly a language with an official interpreter/compiler; rather, it’s a specification, meaning anyone can write a program that implements it. This allows JavaScript to be executed in different places, such as:
- different browsers, like Chrome with the V8 engine or Safari with JavaScriptCore
- on the server, with Node.js and V8 as well.
Engines implement various optimization techniques to make the code run faster, such as just-in-time compilation and inline caching. Now, with the code’s execution being separated from its environment, there needs to be a way for JavaScript to interact with the execution environment. This is the runtime environment. The runtime provides a different set of APIs that make sense for that particular use case, such as executing a shell command exec (‘shutdown -h now’) with Node.js or manipulating DOM elements in the browser.
