Knip it

  • javascript
  • bundle
  • export
  • webpack
2 min read

Achieving small JavaScript bundle sizes is a goal cherished by users, clients, browsers, ISPs, and, not least, developers. While it can be challenging to maintain, optimizing bundle size was the focus of my work this week.

Webpack

In the current JavaScript ecosystem, the spotlight may be on ESM and Vite, but Webpack remains the most popular and widely used bundler. Understanding our roots is key, and Webpack plays a vital role in optimizing bundle size.

Code-splitting & Caching

Webpack organizes our developed code into JavaScript chunks. Executing npm run build reveals the bundling process. By default, Webpack determines which parts go into which bundle, often resulting in a single file. However, this also means our third-party dependencies end up in the same bundle. For optimal performance, it’s beneficial to separate certain dependencies, like React, into their own bundle:

optimization: {
	runtimeChunk: 'single',
	splitChunks: {
		chunks: 'all',
		name: (module, chunks, cacheGroupKey) => `vendors--${chunks.map((chunk) => chunk.name).join('--')}`,
		cacheGroups: {
			react: {
				test: /[\\/]node_modules[\\/](react|react-dom|react-router-dom)[\\/]/,
				name: 'vendor--react',
				chunks: 'all',
			},
		},
	},
},

The browser can cache these bundles if allowed, making it crucial to have deterministic bundle names. Fortunately, this is the default behavior in Webpack. The name and contenthash both play crucial roles, explicitly signaling to the browser when the bundle changes:

output: {
	filename: '[name].[contenthash].bundle.js',
	path: path.resolve(__dirname, 'dist'),
	assetModuleFilename: '[path][name][ext]',
	clean: true,
},

Tree-shaking & Minifing

Webpack is also able to get rid of the unused source code and it wont be part of the production bundle. However, its not an easy task. You can apply obvious configurations such as the following.

mode: 'production',
optimization: {
	minimize: true,
	minimizer: [new TerserPlugin(), new CssMinimizerPlugin()],
},

Webpack might struggle to identify pure code (side-effectless), especially when barrel exporting from a module. Minimizing exports and utilizing named exports can mitigate this.

Knip

Enter knip, a powerful tool to detect unused files, modules, exports, and dependencies in your project. Credit goes to DevtoolsFM. With an easy CLI syntax and numerous plugins, even your configuration or test files are in good hands 😊. The tool provides detailed insights into what can be safely deleted or unexported.

npx knip

Utilize knip effectively to reduce your bundle size and assist Webpack in optimizing the production bundle.

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