Bundle analysis and tree shaking in Vue - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the main purpose of tree shaking in Vue projects?

Tree shaking helps optimize Vue applications by:

A Adding extra debugging information to the bundle

B Automatically updating Vue components when data changes

C Removing unused code from the final bundle to reduce size

D Improving CSS styling by removing unused styles

💡 Hint

Think about how to make your app load faster by cutting down code.

Tree shaking removes code that is not used anywhere in your app, making the bundle smaller and faster to load.

❓ component_behavior

intermediate

What will the bundle size be if you import only one function from a large utility library in Vue?

Consider you import only the debounce function from a large utility library in your Vue component. How does tree shaking affect the bundle size?

A The bundle includes only the <code>debounce</code> function and its dependencies

B The entire utility library is included in the bundle

C No code from the utility library is included

D The bundle size doubles because of the import

💡 Hint

Tree shaking removes unused parts of libraries.

Tree shaking keeps only the imported parts and removes unused code, so only debounce and what it needs are included.

🔧 Debug

advanced

Why does your Vue bundle include unused components despite tree shaking?

You notice your Vue app bundle is large and includes components you never use. Which of these is the most likely cause?

A You used <code>v-if</code> to conditionally render components

B You used dynamic imports with <code>defineAsyncComponent</code>

C You only imported components inside <code>setup()</code> function

D You imported components using a wildcard import like <code>import * as components from './components'</code>

💡 Hint

Think about how imports affect what code is included.

Wildcard imports bring in all exports, so tree shaking cannot remove unused components.

📝 Syntax

advanced

Which import style enables tree shaking in Vue projects?

Select the import statement that allows tree shaking to remove unused code:

A import { ref, reactive } from 'vue'

B import * as Vue from 'vue'

C const Vue = require('vue')

D import Vue from 'vue'

💡 Hint

Tree shaking works best with named imports.

Named imports let bundlers identify exactly what is used and remove unused parts.

❓ state_output

expert

What does the bundle analyzer show after enabling tree shaking in a Vue app?

After enabling tree shaking and analyzing your Vue app bundle, what change will you see in the bundle analyzer report?

A More modules included due to added dependencies

B Smaller bundle size with fewer unused modules visible

C No change in bundle size or modules

D Bundle size increases because of added source maps

💡 Hint

Tree shaking removes unused code, so the bundle should shrink.

The bundle analyzer will show a smaller bundle with fewer unused modules after tree shaking is enabled.

Practice

1. What is the main purpose of tree shaking in a Vue project?

easy

A. To change the app's user interface

B. To remove unused code from the final bundle

C. To increase the size of the app bundle

D. To add more features automatically

Solution

1. Step 1: Understand tree shaking concept

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

2. Step 2: Identify its effect on Vue projects

   In Vue, tree shaking helps make the app faster by removing unused components or functions.

3. Final Answer:

   To remove unused code from the final bundle -> Option B

4. Quick Check:

   Tree shaking = remove unused code [OK]

Hint: Tree shaking cuts unused code to shrink bundles [OK]

Common Mistakes:

• Thinking tree shaking adds features
• Believing it increases bundle size
• Confusing it with UI changes

2. Which of the following is the correct way to enable bundle analysis in a Vue CLI project?

easy

A. Add analyze: true in vue.config.js

B. Use npm run serve --analyze

C. Run vue-cli-service build --report

D. Set treeShake: false in package.json

Solution

1. Step 1: Recall Vue CLI bundle analysis command

   The Vue CLI supports bundle analysis with the --report flag during build.

2. Step 2: Check other options for correctness

   Options A, C, and D are incorrect or invalid ways to enable bundle analysis.

3. Final Answer:

   Run vue-cli-service build --report -> Option C

4. Quick Check:

   Bundle analysis command = build --report [OK]

Hint: Use --report flag with build for analysis [OK]

Common Mistakes:

• Adding unsupported config keys
• Using serve instead of build
• Disabling tree shaking by mistake

3. Given this Vue component import code, what will tree shaking do during production build?

import { ref, reactive, unusedFunc } from 'vue';

export default {
  setup() {
    const count = ref(0);
    const state = reactive({ name: 'Vue' });
    return { count, state };
  }
}

medium

A. All imports including unusedFunc are included in the bundle

B. Only unusedFunc is included, others removed

C. Tree shaking does not affect imports

D. unusedFunc is removed from the final bundle

Solution

1. Step 1: Identify used and unused imports

   The code uses ref and reactive, but unusedFunc is never used.

2. Step 2: Understand tree shaking effect

   Tree shaking removes unused imports like unusedFunc to reduce bundle size.

3. Final Answer:

   unusedFunc is removed from the final bundle -> Option D

4. Quick Check:

   Unused imports removed by tree shaking [OK]

Hint: Unused imports get removed in production build [OK]

Common Mistakes:

• Assuming all imports stay in bundle
• Thinking tree shaking removes used code
• Believing tree shaking is manual

4. You notice your Vue app bundle is larger than expected. Which of these is a likely cause related to tree shaking?

medium

A. You imported entire libraries instead of specific functions

B. You enabled production mode in build

C. You removed unused imports manually

D. You used ref and reactive properly

Solution

1. Step 1: Analyze import style impact on bundle size

   Importing whole libraries (like import * as lodash from 'lodash') prevents tree shaking from removing unused parts.

2. Step 2: Check other options for relevance

   Options B, C, and D either reduce bundle size or are unrelated to bundle size increase.

3. Final Answer:

   You imported entire libraries instead of specific functions -> Option A

4. Quick Check:

   Whole library imports block tree shaking [OK]

Hint: Import only needed parts to enable tree shaking [OK]

Common Mistakes:

• Thinking production mode increases bundle
• Believing manual removal is needed
• Ignoring import style effects

5. You want to reduce your Vue app's bundle size by removing unused components and libraries. Which combination of steps is best?

hard

A. Use dynamic imports for components and enable production build with bundle analysis

B. Import all components globally and disable production optimizations

C. Manually delete unused files without build tools

D. Use development build and avoid code splitting

Solution

1. Step 1: Use dynamic imports to load components only when needed

   This helps tree shaking and code splitting to reduce initial bundle size.

2. Step 2: Enable production build with bundle analysis

   This activates tree shaking and lets you see what code is included to optimize further.

3. Final Answer:

   Use dynamic imports for components and enable production build with bundle analysis -> Option A

4. Quick Check:

   Dynamic imports + production build = smaller bundles [OK]

Hint: Combine dynamic imports and production build for best results [OK]

Common Mistakes:

• Importing all components globally
• Disabling production optimizations
• Relying on manual file deletion