Bundle size analysis in Angular - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is bundle size in Angular applications?

Bundle size is the total size of all the files (JavaScript, CSS, assets) that the browser downloads to run your Angular app. Smaller bundles load faster and improve user experience.

beginner

How can you analyze the bundle size of an Angular app?

You can analyze bundle size using Angular CLI's built-in command ng build --stats-json and then visualize it with tools like Webpack Bundle Analyzer or Source Map Explorer.

intermediate

What is the purpose of lazy loading in reducing bundle size?

Lazy loading splits your app into smaller chunks and loads them only when needed. This reduces the initial bundle size and speeds up the app start time.

intermediate

Name two Angular CLI build options that help reduce bundle size.

1. --prod or --configuration production enables optimizations like minification and tree shaking.
2. --aot (Ahead-of-Time compilation) compiles templates during build to reduce runtime size.

intermediate

What is tree shaking and how does it affect bundle size?

Tree shaking is a process that removes unused code from your final bundle. It helps make the bundle smaller by including only the code your app actually uses.

Which Angular CLI command generates a stats file for bundle analysis?

A ng lint --stats

B ng serve --stats

C ng build --stats-json

D ng test --bundle

The command ng build --stats-json creates a JSON file with bundle info for analysis.

What does lazy loading do in Angular?

A Loads modules only when needed

B Loads all modules at app start

C Removes unused code automatically

D Compresses CSS files

Lazy loading delays loading modules until the user navigates to them, reducing initial bundle size.

Which build option enables Ahead-of-Time compilation?

A --jit

B --watch

C --prod

D --aot

The --aot option compiles templates during build time, reducing runtime size.

What is tree shaking in Angular build process?

A Adding extra code for features

B Removing unused code

C Compressing images

D Loading modules lazily

Tree shaking removes code that is not used in the app to reduce bundle size.

Which tool can visualize Angular bundle size from stats file?

A Webpack Bundle Analyzer

B Angular CLI Serve

C Node Package Manager

D TypeScript Compiler

Webpack Bundle Analyzer helps visualize the contents and size of bundles using the stats JSON.

Explain how you would analyze and reduce the bundle size of an Angular application.

Think about build commands, tools, and Angular features that help optimize size.

Describe the benefits of lazy loading and tree shaking in Angular bundle size optimization.

Focus on how these techniques affect loading and code inclusion.

Practice

1. What is the main purpose of bundle size analysis in Angular applications?

easy

A. To change the app's color scheme

B. To add more features to the Angular app

C. To find which parts of the app make the bundle large

D. To increase the app's loading time

Solution

1. Step 1: Understand bundle size analysis goal

   Bundle size analysis helps identify what parts of the app increase the size of the final build.

2. Step 2: Match purpose with options

   Only To find which parts of the app make the bundle large correctly states the purpose as finding large parts in the bundle.

3. Final Answer:

   To find which parts of the app make the bundle large -> Option C

4. Quick Check:

   Bundle size analysis = find large parts [OK]

Hint: Think: Why check bundle size? To find big parts [OK]

Common Mistakes:

• Confusing bundle size analysis with adding features
• Thinking it changes app appearance
• Assuming it slows down the app

2. Which Angular CLI command generates a JSON file useful for bundle size analysis?

easy

A. ng build --stats-json

B. ng serve --stats-json

C. ng test --stats-json

D. ng lint --stats-json

Solution

1. Step 1: Recall Angular CLI commands for building

   The command to build the app and generate stats is ng build --stats-json.

2. Step 2: Identify correct option

   ng build --stats-json matches the correct command to create the JSON file for bundle analysis.

3. Final Answer:

   ng build --stats-json -> Option A

4. Quick Check:

   Build with stats JSON = ng build --stats-json [OK]

Hint: Build command with --stats-json creates analysis file [OK]

Common Mistakes:

• Using ng serve instead of ng build
• Confusing test or lint commands with build
• Forgetting to add --stats-json flag

3. After running ng build --stats-json, you use source-map-explorer on the generated JSON. What will you see?

medium

A. A list of unused CSS styles

B. A list of errors in your Angular code

C. A report of unit test results

D. A visual map showing which files contribute most to bundle size

Solution

1. Step 1: Understand what source-map-explorer does

   This tool shows a visual breakdown of the bundle, highlighting file sizes.

2. Step 2: Match output with options

   A visual map showing which files contribute most to bundle size correctly describes the visual map of file size contributions.

3. Final Answer:

   A visual map showing which files contribute most to bundle size -> Option D

4. Quick Check:

   source-map-explorer output = visual size map [OK]

Hint: source-map-explorer shows visual file size map [OK]

Common Mistakes:

• Thinking it shows code errors
• Confusing with test reports
• Expecting CSS style reports

4. You ran ng build --stats-json but source-map-explorer shows no data. What is the likely cause?

medium

A. You did not generate the stats JSON file during build

B. You forgot to install source-map-explorer globally

C. You ran ng serve instead of ng build

D. Your Angular app has no components

Solution

1. Step 1: Check if stats JSON file was created

   source-map-explorer needs the stats JSON file generated by ng build --stats-json.

2. Step 2: Identify missing stats JSON as cause

   If the file is missing, source-map-explorer shows no data. This matches You did not generate the stats JSON file during build.

3. Final Answer:

   You did not generate the stats JSON file during build -> Option A

4. Quick Check:

   No stats JSON = no data in explorer [OK]

Hint: Check if stats JSON file exists before using explorer [OK]

Common Mistakes:

• Assuming source-map-explorer must be global
• Confusing ng serve with ng build
• Thinking app components affect stats generation

5. You notice your Angular bundle is very large. Which combination of actions will best reduce the bundle size?

hard

A. Disable Ahead-of-Time compilation and enable source maps

B. Use lazy loading for modules and remove unused imports

C. Add more third-party libraries and increase polyfills

D. Increase the number of components and services

Solution

1. Step 1: Identify techniques to reduce bundle size

   Lazy loading loads modules only when needed, and removing unused imports cuts unnecessary code.

2. Step 2: Evaluate options for reducing size

   Use lazy loading for modules and remove unused imports correctly combines these effective methods. Other options add size or disable optimizations.

3. Final Answer:

   Use lazy loading for modules and remove unused imports -> Option B

4. Quick Check:

   Lazy loading + clean imports = smaller bundle [OK]

Hint: Lazy load and clean imports to shrink bundle [OK]

Common Mistakes:

• Adding more libraries increases size
• Disabling AOT slows app and increases size
• Adding components without optimization