nanobundle

Perfect build tool for libraries, powered by esbuild

Features

Automatic entry points
Support for ESM and CommonJS
Support TypeScript NodeNext moduleResolution
Support multple & complex entries by Node.js's Conditional Exports
Support Import Maps with Node.js's Subpath Imports rule
Optimize esbuild options to maximize concurrency
Only configuration you need is package.json (and optionally tsconfig.json)

Usage

You don't need any config files or passing the entry paths. But only you need to have proper package.json (and tsconfig.json)

{
  "main": "./lib/index.js",
  "scripts": {
    "build": "nanobundle build"
  }
}

That's it, then just run yarn build or npm run build. What a magic ✨

nanobundle is smart enough to automatically determine the location of the appropriate source files from the entries specified in your package.json.

It searches based on the --root-dir and --out-dir on the CLI flags (defaults to src and lib) but respects tsconfig.json if present.

`package.json` Recipes

More interestingly, it supports all of Node.js' notoriously complex Conditional Exports rules.

The ESM-only approach

{
  "type": "module",
  "main": "./lib/index.js",    // => src/index.ts
  "module": "./lib/index.js",  // => src/index.ts
  "exports": "./lib/index.js"  // => src/index.ts
}

Dual-package exports

{
  "exports": {
    ".": {
      "types": "./lib/index.d.ts",     // => src/index.ts
      "require": "./lib/index.js",     // => src/index.ts
      "import": "./lib/index.mjs"      // => src/index.mts or src/index.ts
    },
    "./package.json": "./package.json" // => package.json
  }
}

Mutliple platform support

{
  "exports": {
    ".": {
      "node": {
        "require": "./lib/index.node.cjs",  // => src/index.cts or src/index.ts
        "import": "./lib/index.node.mjs"    // => src/index.mts or src/index.ts
      },
      "deno": "./lib/index.deno.mjs",       // => src/index.mts or src/index.ts
      "browser": "./lib/index.browser.mjs", // => src/index.mts or src/index.ts
      "default": "./lib/index.js"           // => src/index.ts
    },
    "./package.json": "./package.json"      // => package.json
  }
}

Server/Client submodules

{
  "exports": {
    ".": "./lib/common.js",          // => src/common.ts
    "./server": {
      "types": "./lib/server.d.ts",  // => src/server.ts
      "require": "./lib/server.cjs", // => src/server.cts or src/server.ts
      "import": "./lib/server.mjs"   // => src/server.mts or src/server.ts
    },
    "./client": {
      "types": "./lib/client.d.ts",      // => src/client.ts
      "require": "./lib/client.min.cjs", // => src/client.cts or src/client.ts, output will be minified:sparkles:
      "import": "./lib/client.min.mjs"   // => src/client.mts or src/client.ts, output will be minified
    },
    "./package.json": "./package.json"
  }
}

Development-only code for debugging

{
  "exports": {
    "development": "./dev.js",     // => src/dev.ts
    "production": "./index.min.js" // => src/index.ts, output will be minified
  }
}

CLI Options

Full CLI options

Usage
  $ nanobundle <command> [options]

Available Commands
  build    Build once and exit
  clean    Remove outputs

Options
  --version            Display current version

  --cwd                Use an alternative working directory
  
  --clean              Clean outputs before build

  --tsconfig           Specify the path to a custom tsconfig.json

  --import-maps        Specify import map file path (default: package.json)

  --root-dir           Specify the path to resolve source entry (default: ./src)
                       This also can be configured by tsconfig.json

  --out-dir            Specify the path to resolve source entry (default: ./lib)
                       This also can be configured by tsconfig.json

  --platform           Specify bundle target platform (default: "netural")
                       One of "netural", "browser", "node" is allowed

  --standalone         Embed external dependencies into the bundle (default: false)

  --external           Specify external dependencies to exclude from the bundle

  --jsx                Specify JSX mode. One of "transform", "preserve", "automatic" is allowed
                       This also can be configufeature comparisonred by tsconfig.json

  --jsx-factory        Specify JSX factory (default: "React.createElement")
                       This also can be configured by tsconfig.json

  --jsx-fragment       Specify JSX <Fragment> factory (default: "Fragment")
                       This also can be configured by tsconfig.json

  --jsx-import-source  Specify JSX import source (default: "react")
                       This also can be configured by tsconfig.json

  --no-sourcemap       Disable source map generation

  --no-legal-comments  Disable legal comments generation

  --no-bundle          Disable ESBuild bundle and other files build

  --no-dts             Disable TypeScript .d.ts build

  --verbose            Set to report build result more verbosely

  --help               Display this message

Features

Nanobundle believes the package.json today is expressive enough for most module use cases.

So attempting to turn users' attention back to the Node's package spec like ES Modules and Import Maps which are already supported by Node.js, rather than adding another customizing options.

Automatic entry points

You don't need to pass or set entry points in any configuration file, only you have to do is provide correct exports in your package.json.

nanobundle will automatically search for entry files in the rootDir and outDir you have. (defaults are src and lib, or respectively configurable by tsconfig.json or CLI arguments)

{
  "main": "./lib/index.js",         // => search src/index.cts, src/index.ts, etc
  "module": "./lib/index.mjs",      // => search src/index.mts, src/index.ts, etc
  "exports": {
    "./feature": "./lib/feature.js" // => search src/feature.cts, src/feature.ts, etc
  }
}

Build targets

nanobundle expects you to write a Web-compatible(netural) package.

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

Pass --platform=node flag
Set the entry point with node condition.

Without engines field in package.json, the default Node.js version will be v14.

Conditional Exports

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

See Node.js docs for more detail.

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

You can use conditional exports for dealing with Dual Package Hazard.

E.g. for supporting both CommonJS and ESM package.

{
  "exports": {
    "require": "./lib/index.cjs",
    "import": "./lib/index.mjs"
  }
}

Import Maps

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/",
  }
}

nanobundle also handles Node.js's Subpath Imports rules.

{
  "imports": {
    "#dep": {
      "node": "dep-node-native",
      "default": "./dep-polyfill.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.

nanobundle automatically generate TypeScript declaration as you specify types entries in the package.json, or you can disable it passing --no-dts flag.

Minification

Any entires with .min.(c|m)?js will generate minified output.

{
  "exports": "./index.min.js"  // will be minifies output
}

Using `process.env.NODE_ENV` with condition

Conditional entries with Node.js community condition production or development will be built with injected process.env.NODE_ENV as its value.

{
  "exports": {
    ".": {
      "development": "./dev.js",     // process.env.NODE_ENV === 'development'
      "production": "./prod.min.js"  // process.env.NODE_ENV === 'production'
    }
  }
}

Feature Comparison

Build tool	0 Config	Respect `package.json`	TypeScript `.d.ts` generation	Concurrency	Multiple Entries	Conditional Exports	Import Maps	CSS Support	Plugins	Dev(watch) mode
nanobundle	✔️	✔️	✔️	✔️	✔️	✔️	✔️	✔️	✖️ (planned)	✖️ (planned)
microbundle	✔️	✔️	✔️	✔️	✖️	🟡 (only flat)	✖️	✔️	✖️	✔️
tsup	🟡 (mostly by custom file)	✖️	✔️	✔️	✔️	✖️	🟡 (with plugin)	🟡 (experimental)	✔️	✔️
estrella	✖️	✖️	✔️	✔️	✖️	✖️	✖️	✖️	✖️	✔️
esbuild	✖️	✖️	✖️	✔️	✔️	✖️	✖️	✔️	✔️	✔️
Rollup	✖️	✖️	🟡 (with plugin)	✔️	✔️	🟡 (by code)	🟡 (with plugin)	✔️	✔️	✔️
Vite (lib mode)	✖️	✖️	🟡 (with plugin)	✔️	✔️	🟡 (by code)	🟡 (with plugin)	✔️	✔️	✔️
Parcel (lib mode)	✔️	✔️	✔️	✔️	✖️	✖️	✖️	✔️	✖️	✔️