nanobundle

Yet another build tool for libraries, powered by esbuild

Features

• Support for ESM and CommonJS
• Support Import Maps
• Find and optimize the esbuild options for you
• Only configuration you need is package.json (and optionally tsconfig.json)

Installation

1. Install by running yarn add -D nanobundle or npm i -D nanobundle

2. Setup your package.json:

   {
     "name": "your-package-name",
   
     "source": "./src/foo.ts",        // required, the entry source file
   
     "module": "./dist/foo.mjs",    // where to generate the ESM bundle
     "main": "./dist/foo.cjs",      // where to generate the main entry (CommonJS by default, or ESM if `"type": "module"` and not `*.cjs`)
   
     "imports": {                   // import maps for modules/paths alias
       // ...
     },
   
     "exports": {                   // export maps for multiple/conditional entries
       // ...
     },
   
     "scripts": {
       "build": "nanobundle build"  // compiles "source" to "main"/"module"
     }
   }

3. Try it out by running yarn build or npm run build

Usage & Configuration

nanobundle is heavily inspired by microbundle, but more daring to try to remove the configuration much as possible. I believe the package.json today is complex enough and already contains most of the configuration for common module use cases.

So attempting to turn users' attention back to the Node's package spec and some meaningful proposals like ES Modules and Import maps which are already supported by Node.js, rather than another custom configuration.

Build targets

nanobundle expects you to write a Web-compatible package.

If you use any Node.js APIs, you need to tell it explicitly via:.

• Set the entry point with .cjs or .node extension
• Specify Node.js version via engines field in the package.json

Without engines, the default target will be Node.js v14.

Import Map

nanobundle supports Import maps

You can specify import alias by your package.json, or by a separated json file with the --import-map option.

{
  "imports": {
    "~/": "./",
    "@util/": "./src/utils/",

    // Node.js-style conditional imports
    "#dep": {
      "default": "./dep-polyfill.js",
      "node": "dep-node-native"
    }
  }
}

Export Map

You can specify multiple/conditional entry points in your package.json.

See Node.js docs for more detail.

{
  "type": "module",
  "main": "./main.js",
  "exports": {
    ".": "./main.js",
    "./feature": {
      "default": "./feature.js",
      "node": "./feature-node.js"
    }
  }
}

Embedding dependencies

nanobundle by default does nothing about external like dependencies and peerDependencies.

However, if the --standalone flag is set, it will try to embed all external dependencies into the bundle.

Dependencies specified with --external and Node.js internal APIs are always excluded.

TypeScript

Given a tsconfig.json file in the cwd or --tsconfig option, nanobundle looks for options for TypeScript and JSX.

You can specify declarationDir in your tsconfig, or nanobundle infer the dir from types entry.

nanobundle automatically generate TypeScript declaration as you specify types entry in the package.json, or you can disable it passing --dts=false argument.

Alternatives

• microbundle : Rollup wrapper that provides similar concept
• esbuild : This is a simple esbuild wrapper so you can get similar results with just esbuild alone
• estrella : Build tool based on esbuild
• tsup : Zero-config bundler based on esbuild

License

MIT