Bun the new js run time

Bun is a superfast all in one toolkit for javascript an typescript apps. Bun streamline the dev process making it smoother and more efficient, it is not just a runtime but also a bundler package manager and test runner.

Bun vs Node as a JavaScript Runtime

A js run time is an environment which provides all the necessary components in order to use and run a js program.Both node and bun are a javascript run time. Node js is written in c++ and Bun is written in general purpose programming language zig.

A javascript Engine is basically a program that converts a js program in to machine code. Node js uses Google's v8 engine and Bun uses Javascript core which is an opensource developed by apple for safari.

Both v8 and JSC (Javascript core) works very differently. jsc prioritize faster start times and reduced memory usage with a slightly slower execution time. On the other hand v8 prioritize fast execution with more run time optimization which may lead to more memory usage whhich makes Bun more efficient and smoother

Transpiler

To execute typescript in node env external dependecies are required. one common approach is the build step to transpile ts into js and then run resulting js code(npm i -D typescript ts-node) Bun comes with a javascript transpiler integrated into the runtime directlly run js ts jsx or tsx file.This is also a big reason for using bun over node.

Module system

A module system allows developers to organize code into reusable segments. Javascript mainly uses common js and ESM i.e Ecmascript module.

Common js is used on server such as node js server uses require or module.exports for synchronous module handelling. Esm for browsers uses import and export statement providing more static and asynchronous approach optimized for browser builds.

The main point to note here is that you can not use module and import statement side by side in the same file and one more thing to use import in a file you should create a file using mjs extension or set type to module in package.json file which is in root directory in your project.

On the other hand bun support both common js and esm without any special configuration i.e you can use both import and require in same file.

Web Api's

Integral to browser based application and offer tools like fetch and websocket for web application.Earlier fetch was not supported in node js developers have to rely on packages such as node-fetch but from node js v18 there is experimental support for the fetch api but bun has built support to fetch. Dev can directly use fetch request response.

Hot reloading

Hot Reloading is that feature that instantly reflects code changes in the application without the need of full restart in node js we have a couple of options for hot reloading for example nodemon that hard restarts the entire process and from node18 we have --watch flag for the same.

Bun has a --hot flag. unlike the node js methods that might require a full process restart bun reloads your code in place without terminating the old process provides a smoother development experience.

Node js compatibility

• Bun is actually drop in replacement for node.js
• You can integrate bun with node js app without any modification
• There is already support for built-in node js module such as fs path and net
• Adherence to the nodejs module resolution algorithm, including the familiar node_modules structure

Bundler

Bundling is the process of taking multiple js files and merging them into one or more optimized bundles.Process may inivolve transformation such as converting typescript to javascript or minifying the code to reduce its size. In node js eco system bundelling is typically handeled by third party tools such as webpack rollup parcel rather than node js itself.

Bun on the other hand is designed to bundle js and ts code for various platfroms.To bundle with bun use simple command bun build ./index.ts --outdir ./build.

Bundler

Bun boasts installation speed which is faster than npm. It acheives this by the help of global module cache, eliminating redundant downloads from the npm registry Bun enusres fastest sysytem call and it also gives optimal performance.