The zero-configuration bundler for tiny modules, powered by Rollup.
- One dependency to bundle your library using only a
package.json - Support for ESnext & async/await (via Bublé & async-to-promises)
- Produces tiny, optimized code for all inputs
- Supports multiple entry modules (
cli.js+index.js, etc) - Creates multiple output formats for each entry (CJS, UMD & ESM)
- 0 configuration TypeScript support
- Built-in Terser compression & gzipped bundle size tracking
npm i -D microbundle
{
"source": "src/foo.js", // Your source file (same as 1st arg to microbundle)
"main": "dist/foo.js", // output path for CommonJS/Node
"module": "dist/foo.mjs", // output path for JS Modules
"unpkg": "dist/foo.umd.js", // optional, for unpkg.com
"scripts": {
"build": "microbundle", // uses "source" and "main" as input and output paths by default
"dev": "microbundle watch"
}
}Microbundle now has a new modern format (microbundle -f modern).
Modern output still bundles and compresses your code, but it keeps useful syntax
around that actually helps compression:
// Our source, "src/make-dom.js":
export default async function makeDom(tag, props, children) {
const el = document.createElement(tag);
el.append(...(await children));
return Object.assign(el, props);
}Microbundle compiles the above to this:
export default async (e, t, a) => {
const n = document.createElement(e);
return n.append(...(await a)), Object.assign(n, t);
};This is enabled by default - all you have to do is add the field to your package.json. You might choose to ship modern JS using the "module" field:
{
"main": "dist/foo.umd.js", // legacy UMD bundle (for Node & CDN's)
"module": "dist/foo.modern.mjs", // modern ES2017 bundle
"scripts": {
"build": "microbundle src/foo.js -f modern,umd"
}
}Microbundle includes two commands - build (the default) and watch. Neither require any options, but you can tailor things to suit your needs a bit if you like.
Unless overridden via the command line, microbundle uses the source property in your package.json to locate the input file, and the main property for the output.
For UMD builds, microbundle will use a snake case version of the name field in your package.json as export name. This can be overridden either by providing an amdName key in your package.json or via the --name flag in the cli.
Acts just like microbundle build, but watches your source files and rebuilds on any change.
Just point the input to a .ts file through either the cli or the source key in your package.json and you’re done.
You can specify output builds in a package.json as follows:
"main": "dist/foo.js", // CJS bundle
"umd:main": "dist/foo.umd.js", // UMD bundle
"module": "dist/foo.m.js", // ES Modules bundle
"source": "src/foo.js", // custom entry module (same as 1st arg to microbundle)
"types": "dist/foo.d.ts", // TypeScript typings
Use the --visualize flag in the cli to generate a stats.html file at build time, showing the sizes of the files that are included in your bundled output. Uses rollup-plugin-visualizer.
Libraries often wish to rename internal object properties or class members to smaller names - transforming this._internalIdValue to this._i. Microbundle doesn't currently do this by default, but it can be enabled by adding a "mangle" property to your package.json, with a pattern to control when properties should be mangled. To mangle all property names beginning an underscore, add the following:
{
"mangle": {
"regex": "^_"
}
}Usage
$ microbundle <command> [options]
Available Commands
build Build once and exit
watch Rebuilds on any change
For more info, run any command with the `--help` flag
$ microbundle build --help
$ microbundle watch --help
Options
-v, --version Displays current version
-i, --entry Entry module(s)
-o, --output Directory to place build files into
-f, --format Only build specified formats (default modern,es,cjs,umd)
-w, --watch Rebuilds on any change (default false)
--target Specify your target environment (node or web) (default web)
--external Specify external dependencies, or 'none'
--globals Specify globals dependencies, or 'none'
--define Replace constants with hard-coded values
--alias Map imports to different modules
--compress Compress output using Terser
--strict Enforce undefined global context and add "use strict"
--name Specify name exposed in UMD builds
--cwd Use an alternative working directory (default .)
--sourcemap Generate source map (default true)
--raw Show raw byte size (default false)
--jsx A custom JSX pragma like React.createElement (default: h)
--tsconfig Specify the path to a custom tsconfig.json
--visualize Generate bundle size visualization (stats.html)
-h, --help Displays this message
Examples
$ microbundle build --globals react=React,jquery=$
$ microbundle build --define API_KEY=1234
$ microbundle build --alias react=preact
$ microbundle watch --no-sourcemap # don't generate sourcemaps
$ microbundle build --tsconfig tsconfig.build.json
Here's what's coming up for Microbundle:
- Preact Fast 3kB React alternative with the same modern API. Components & Virtual DOM.
- Stockroom Offload your store management to a worker easily.
- Microenvi Bundle, serve, and hot reload with one command.
- react-recomponent Reason-style reducer components for React using ES6 classes.
- brazilian-utils Utils library for specific Brazilian businesses.
- react-hooks-lib A set of reusable react hooks.
- mdx-deck-live-code A library for mdx-deck to do live React and JS coding directly in slides.
- react-router-ext An Extended react-router-dom with simple usage.
- routex.js A dynamic routing library for Next.js.