Check the sizes of your code-splitted bundles. Any file, a lot of predefined rules and fully customized rules can be added.

Motivation

Since the beginning days, my number one choice was Bundlesize. Not because it is very customizable, but it worked.

While the number of mobile devices is increasing and performance is crucial to a lot of companies, bundles get split in several files.

This lead to more problems with bundlesize, because one can only specify a maxSize which was not sufficient to me anylonger.

Install

yarn add bundlecheck --dev
npm install bundlecheck --save-dev

Get Started

All sizes are in KiloByte

Create a basic configuration file with the following content in the root of your project and call it .bundlecheck.config.js.

module.exports = {
  relativeTo: '.',
  cwd: '.',
  observe: [
    {
      paths: ['**'],
      rules: [{ every: [0.01, 0.5] }],
    },
  ],
}

Inside your package.json add this to your scripts section:

  "scripts": {
    "bundlecheck": "bundlecheck"
  }

CLI Options

Specify a config file: --configfile or -cf

Documentation

General Configuration

• cwd Specifies a root folder from where to find all paths
• relativeTo Used to make cwd relative to this specified path
• observe An array of observable paths on which rules can be applied
• rules: An array of rules that are tested against every entry in observe
• ignore: An array of fast-glob paths that should be ignored

Observe Entry Configuration

Use a predefined check function

observe: [
  {
    paths: ['**.js'] // Use glob patter (fast-glob)
    rules: [
      every: [0.1, 5], // Any file matched has to be between 100 Bytes and 5 KiloBytes big
      sum: [0.001], // The sum of all matching files has to be exactly 1 Byte
      mean: [,0.05], // Averaging matched file sizes have to be below 50 Bytes
      deviation [1, 2] // Defining the standard deviation of all matched files, so there has to be a difference between all files between 1 and 2 KiloByte
    ]
  }
]

Defining a custom check function

Multiple rules inside of one observe entry are treated with a boolean AND.

observe: [
  {
    paths: ['**.js']
    rules: [
      () => ({
        result: true,
        message: 'This will always result to true',
      }),
      (sizeMap) => {
        const result = sizeMap.reduce((s, [path, size]) => s + size, 0) <= 0.2;
        return {
          result,
          message: result ? 'All Good' :
            `Sum of files ${sizeMap.map(([ name ]) => name).join(' ')} too big`,
        }
      },
    ]
  }
]

Example Configurations

NextJS

Contents of a configuration file used within NextJS

const fs = require('fs');

const buildId = fs.readFileSync('dist/BUILD_ID', 'utf8');

module.exports = {
  relativeTo: '.',
  cwd: 'dist',
  observe: [
    {
      paths: [`server/static/${buildId}/pages/**.js`],
      rules: [{ every: [0, 65] }]
    },
    {
      paths: [`static/css/**.css`],
      rules: [{ every: [0, 2.5], sum: [0, 3] }]
    },
    {
      paths: [`static/chunks/!(commons)*.js`],
      rules: [{ every: [0, 0.2] }]
    },
    {
      paths: [`static/chunks/commons*.js`],
      rules: [{ every: [0, 235] }]
    },
    {
      paths: [`static/${buildId}/pages/!(_app)*.js`],
      rules: [{ every: [0, 100], sum: [0, 120] }]
    },
    {
      paths: [`static/${buildId}/pages/_app.js`],
      rules: [{ every: [120, 130] }]
    },
    {
      paths: ['static/runtime/main-*.js', 'static/runtime/polyfills-*.js', 'static/runtime/webpack-*.js'],
      rules: [{ every: [0, 15], sum: [20, 25] }]
    },
  ],
};

Yet to come

The following features are planned:

• Fully log successes and errors (currently only errors are displayed)
• Create a Webpack loader in order to integrate Bundlecheck within the build process
• Compare measured size against last build on a specific branch
• Make use of Github PR checks
• Support other config file formats than JS