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React Academy · Lesson

Bundle Analysis & Trimming Unused Code

Read bundle reports, find big modules, and trim them with tree-shaking friendly code: ESM named exports, no top-level side effects, lazy where sensible.

Bundle Analysis & Trimming Unused Code is a free React Academy lesson on CoddyKit — lesson 2 of 3. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the React Academy learning path, one of 3 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Why analyze bundles?

Goal: Slim your bundle.

  • Read bundle reports
  • Adopt tree-shakeable ESM
  • Lazy-load rare screens

Signals in reports

  • Big deps (charts, date libs)
  • Duplicate versions
  • Top-level side effects
  • Default imports that pull whole packages

Named exports, no side effects

Prefer named exports and keep modules pure (no side effects on import).

<div id="root"></div>

No top-level side effects

Avoid side effects at import time; expose functions and call them after import.

<div id="root"></div>

Lazy load with React.lazy

Lazy-load rare screens to keep the initial bundle tiny; show a small fallback.

<div id="root"></div>

Tips & checklist

  • Use ESM named exports
  • Keep modules pure (no import-time work)
  • Lazy-load rare routes/widgets
  • Prefer smaller alternatives (e.g., dayjs over moment)

Tree-shaking basics check

Which change most helps bundlers tree-shake unused code?

Recap

Recap: Read bundle reports, switch to ESM named exports, remove import-time side effects, and lazy-load rare screens to keep the initial bundle lean.

Frequently asked questions

Is the “Bundle Analysis & Trimming Unused Code” lesson free?

Yes — the full text of “Bundle Analysis & Trimming Unused Code” is free to read here on the web, and the React Academy course includes 3 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the React Academy course, upgrade to CoddyKit PRO.

What will I learn in “Bundle Analysis & Trimming Unused Code”?

Read bundle reports, find big modules, and trim them with tree-shaking friendly code: ESM named exports, no top-level side effects, lazy where sensible. You practise React Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start React Academy?

No prior experience is required. React Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 3, so you can start here or from the beginning and move at your own pace.

How long does the “Bundle Analysis & Trimming Unused Code” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this React Academy lesson?

Yes. Every React Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Dev/Prod Builds, Source Maps, Envs
  2. Bundle Analysis & Trimming Unused Code
  3. Basic CI: Lint → Test → Build
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