unenv

What is unenv?

The 'unenv' npm package is designed to provide a universal environment for JavaScript and TypeScript projects. It allows developers to create isomorphic code that can run seamlessly in both Node.js and browser environments by providing polyfills and shims for various APIs.

What are unenv's main functionalities?

Polyfills for Node.js APIs

This feature provides polyfills for Node.js APIs, allowing you to use Node.js-specific features in a browser environment. The code sample demonstrates how to use the Buffer API from Node.js in a universal environment.

const { Buffer } = require('unenv/runtime/polyfills/buffer');
const buffer = Buffer.from('Hello, world!');
console.log(buffer.toString('utf-8'));

Environment Detection

This feature allows you to detect the current environment (Node.js or browser) and execute code conditionally based on that. The code sample shows how to check if the code is running in Node.js or a browser.

const { isNode, isBrowser } = require('unenv');
if (isNode) {
  console.log('Running in Node.js');
} else if (isBrowser) {
  console.log('Running in the browser');
}

Universal Fetch API

This feature provides a universal Fetch API that works in both Node.js and browser environments. The code sample demonstrates how to make a fetch request and handle the response.

const fetch = require('unenv/runtime/polyfills/fetch');
fetch('https://api.example.com/data')
  .then(response => response.json())
  .then(data => console.log(data));

Other packages similar to unenv

isomorphic-fetch

The 'isomorphic-fetch' package provides a Fetch API implementation that works in both Node.js and browser environments. It is similar to the Fetch API polyfill provided by 'unenv', but it focuses solely on fetch functionality.

universal-env

The 'universal-env' package helps in detecting the current environment (Node.js or browser) and provides utility functions for environment-specific code. It is similar to the environment detection feature of 'unenv'.

node-polyfill-webpack-plugin

The 'node-polyfill-webpack-plugin' package provides polyfills for Node.js core modules in a Webpack environment. It is similar to the polyfills provided by 'unenv', but it is specifically designed for use with Webpack.

README

unenv

unenv provides a collection of Node.js and Web polyfills and mocking utilities with configurable presets for converting JavaScript code and libraries to be platform and runtime agnostic, working in any environment including Browsers, Workers, Node.js, Cloudflare Workers, Deno.

Unenv is used by Nitro and Nuxt today.

[!NOTE] You are on the development (v2) branch. Check out v1 for the current release.

Install

# ✨ Auto-detect
npx nypm install -D unenv

# npm
npm install -D unenv

# yarn
yarn add -D unenv

# pnpm
pnpm install -D unenv

# bun
bun install -D unenv

# deno
deno install --dev unenv

Usage

Using env utility and built-in presets, unenv will provide an abstract configuration that can be used in bundlers (rollup.js, webpack, etc.).

import { env } from "unenv";

const { alias, inject, polyfill, external } = env({}, {}, {});

Note: You can provide as many presets as you want. unenv will merge them internally and the right-most preset has a higher priority.

Presets

node

(view source)

Suitable to convert universal libraries working in Node.js.

• Add supports for global fetch API
• Set Node.js built-ins as externals

import { env, node } from "unenv";

const envConfig = env(node, {});

nodeless

(view source)

Suitable to transform libraries made for Node.js to run in other JavaScript runtimes.

import { env, nodeless } from "unenv";

const envConfig = env(nodeless, {});

Built-in Node.js modules

unenv provides a replacement for Node.js built-in modules compatible with any runtime.

• ✅ node:assert
• ✅ node:assert/strict
• ✅ node:async_hooks
• ✅ node:buffer
• ✅ node:child_process
• ✅ node:cluster
• ✅ node:console
• ✅ node:constants
• ✅ node:crypto
• ✅ node:dgram
• ✅ node:diagnostics_channel
• ✅ node:dns
• ✅ node:dns/promises
• ✅ node:domain
• ✅ node:events
• ✅ node:fs
• ✅ node:fs/promises
• ✅ node:http
• ✅ node:http2
• ✅ node:https
• ✅ node:inspector
• 🚧 node:inspector/promises
• ✅ node:module
• ✅ node:net
• ✅ node:os
• ✅ node:path
• ✅ node:path/posix
• ✅ node:path/win32
• ✅ node:perf_hooks
• ✅ node:process
• ✅ node:punycode
• ✅ node:querystring
• ✅ node:readline
• ✅ node:readline/promises
• 🚧 node:repl
• 🚧 node:stream
• ✅ node:stream/consumers
• ✅ node:stream/promises
• ✅ node:stream/web
• ✅ node:string_decoder
• ✅ node:sys
• ✅ node:timers
• ✅ node:timers/promises
• ✅ node:tls
• ✅ node:trace_events
• ✅ node:tty
• ✅ node:url
• ✅ node:util
• ✅ node:util/types
• ✅ node:v8
• ✅ node:vm
• ✅ node:wasi
• ✅ node:worker_threads
• 🚧 node:zlib

(view source)

Package replacements

unenv provides a replacement for common npm packages for cross-platform compatibility.

(view source)

Manual mocking utils

// Magic proxy to replace any unknown API
import MockProxy from "unenv/runtime/mock/proxy";

// You can also create named mocks
const lib = MockProxy.__createMock__("lib", {
  /* overrides */
});

(view source)

Other polyfills

To discover other polyfills, please check ./src/runtime.

Nightly release channel

You can use the nightly release channel to try the latest changes in the main branch via unenv-nightly.

If directly using unenv in your project:

{
  "devDependencies": {
    "unenv": "npm:unenv-nightly"
  }
}

If using unenv via another tool (Nuxt or Nitro) in your project:

{
  "resolutions": {
    "unenv": "npm:unenv-nightly"
  }
}

License

Published under the MIT license. Made by @pi0 and community 💛

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