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6.0.8 • Public • Published

klap 👏

a zero config, zero dependency bundler for tiny javascript packages.

Build Status David David npm NPM All Contributors

klap output


  • 🎉 zero config: bundle your library using only a package.json
  • 💥 zero config: typescript support (just rename *.js to *.ts)
  • 🌟 zero config: code transforms using babel macros
  • 🌈 zero config: code generation using babel plugin codegen
  • 🚀 zero dependency: uses gcc-style bundling.
  • 🐙 creates tiny bundles for multiple output formats cjs, esm and umd
  • 🔥 Modern JS syntax with class properties, async/await, and generators
  • Built in Minification and Gzip Size Tracking
  • 🌀 Built in development server for quick prototyping.
  • 🎊 Supports react, styled-components and emotion out of the box.

💪 Powered By

  • rollup - Next-generation ES module bundler
  • babel - The compiler for next generation JavaScript

🍽️ Usage

First, initialize your project using klap init:

npx klap init

Prefer Typescript ? initialize using ts argument:

npx klap init ts

Want to use JSX with Typescript? init using tsx argument:

npx klap init tsx

The init command will create a minimal package.json with source, main, module and browser entries and the build, watch and start scripts.

  "name": "...",
  "version": "0.0.0",
  "files": [ "dist" ],
  "source": "src/sum.js",         # source file of your package
  "main": "dist/sum.cjs.js",      # commonjs bundle target
  "module": "dist/sum.esm.js",    # esm bundle target
  "browser": "dist/sum.js",       # umd bundle target
  "scripts": {
    "build": "klap build",        # bundle your package
    "watch": "klap watch",        # bundle your package and watch for changes
    "start": "klap start",        # start a development server
  "devDependencies": {
    "klap": "3.2.0"               # klap as dev dependency

Note: Dropping pkg.main will disable cjs output, also applies to esm and umd outputs.

Then use npm run or yarn to invoke npm scripts as you normally would.

See examples for common use cases using klap.

💢 Granular Control

klap uses sensible defaults for most part. However, as needed, use below properties in package.json to fine tune klap. You can also use cli flags to control config options for klap.

option cli flag(s) description default
source -s --source source file to compile and bundle src/index.js
cjs -c --cjs the output file for common js format pkg.main
esm -e --esm the output file for esm format pkg.module
umd -u --umd the output file for umd format pkg.browser
types -t --types the output file for type definitions pkg.types
browserslist -b --browserslist browserslist compatible compilation target last 2 versions modern browsers if usage is greater than 1%
klap.name -n --name package name for umd bundles sanitized pkg.name
klap.port -p --port port for development server 1234
klap.example --example location of index js/ts file for start command public/index.js or pkg.source
klap.fallback --fallback location of index html file for start command public/index.html
klap.target --target target for development server (umd, es) es
klap.sourcemap --no-sourcemap sourcemaps for builds true
klap.minify --no-minify minification for builds true
klap.runtime --runtime the runtime for new JSX transform react
klap.globals global names for umd bundles {}

🥂 License

klap is licensed under the MIT License.

Documentation is licensed under Creative Common License.

Created with ❤️ by @osdevisnot and all contributors.


Thanks goes to these wonderful people (emoji key):

v 1 r t l


Daniel Berner


Tom Julius


Marcus Lindblom


This project follows the all-contributors specification. Contributions of any kind welcome!

💝 Supporters




npm i klap

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