tree-shaking-and-dead-code-elimination

Tree Shaking and Dead Code Elimination in TypeScript:

• Understanding Tree Shaking:

  Tree shaking is a term commonly used in the context of JavaScript tooling to describe the process of removing unused code (dead code) from the final bundle during the build process.

• ES Modules:

  Use ES6 module syntax (import and export) instead of CommonJS modules (require, module.exports), as the static structure of ES6 modules is what enables tree shaking.

• Side Effects:

  Understand the sideEffects property in package.json. Marking a file or module as side-effect-free helps bundlers like Webpack to safely exclude it from the final bundle if it's not used.

• Pure Annotations:

  Use /*@__PURE__*/ or /*#__PURE__*/ annotations to help tools like UglifyJS and Terser identify pure functions that can be safely removed if not used.

• Bundling Tools:

  Be familiar with bundling tools that support tree shaking, such as Webpack, Rollup, or Parcel, and understand their respective configurations for optimizing tree shaking.

• Production Builds:

  Tree shaking generally occurs during a production build, so ensure that your build process includes a production mode that enables these optimizations.

• TypeScript Configuration:

  In tsconfig.json, use "module": "esnext" to keep the ES6 module syntax intact when TypeScript compiles the code, as bundlers need this format for tree shaking.

• Minifiers:

  Use minifiers like Terser in your build process, which can remove dead code as well as minify your code.

• Unused Export Identification:

  Tools like ts-prune can help identify unused exports in your TypeScript project before runtime, which can be a part of cleaning up the codebase.

• Dynamic Imports:

  Utilize dynamic imports with import() syntax for code-splitting, which also helps in tree shaking by creating separate chunks that can be loaded on demand.

• Avoiding Index Files:

  Be cautious with index files that re-export from multiple modules, as they can inadvertently lead to retaining unused code.

• Analyzing Bundle:

  Use bundle analysis tools like Webpack Bundle Analyzer to visualize the size of the webpack output files and understand how much code is being included in your bundles.

• Code Splitting:

  Alongside tree shaking, implement code splitting to further reduce the size of individual bundles loaded by splitting the code into various bundles which can be loaded on demand.

• Refactoring for Tree Shaking:

  Refactor your code to use named exports instead of default exports, as they are more statically analyzable and thus more amenable to tree shaking.

• Dependency Management:

  Be mindful of third-party libraries' tree shaking compatibility. Prefer libraries that are modular and export their functionality in a tree-shakable manner.

• Avoiding Monolithic Structures:

  Structure your codebase with small, focused modules instead of large monolithic ones to enhance the effectiveness of tree shaking.