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Dead Code Elimination

Overview

Removing unused code reduces bundle size and maintenance burden.

Procedure

1. Automated Detection (Knip)

Knip is a powerful tool to find unused files, dependencies, and exports.

# Install
npm install --save-dev knip

# Run analysis
npx knip

2. TypeScript-Specific Audit (ts-prune)

Find unused exports in your TypeScript files.

# Run directly with npx
npx ts-prune | grep -v "(used in module)"

3. Bundler Tree Shaking

Ensure your package.json and bundler config (Vite/Webpack) support tree shaking.

  • Set "sideEffects": false in package.json for libraries that don't have side effects.
  • Use ES Modules (import/export) instead of CommonJS (require).

4. Manual Review

  • Search for Usage: Before deleting, use grep or IDE search to verify no dynamic references exist.
  • Delete and Test: Delete the code, run the full test suite, and check for runtime errors.

Constraints

  • Side Effects: Be careful with code that has side effects (e.g., global polyfills, CSS imports).
  • Dynamic Access: Tools might miss code accessed via dynamic strings (e.g., eval or object[someVar]).
  • Dependencies: Don't just delete code; also remove unused packages from package.json (npm uninstall).

Expected Output

A leaner codebase with reduced bundle sizes, faster build times, and less "noise" for developers to maintain.