Performance auditing with Lighthouse in Astro - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import Lighthouse in an Astro project.

Astro

import [1] from 'lighthouse';

Drag options to blanks, or click blank then click option'

Alighthouse

BrunLighthouse

CLighthouse

Daudit

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect capitalization in the import name.

Trying to import a function that does not exist.

The correct import name is lighthouse to use the Lighthouse API in your Astro project.

2fill in blank

medium

Complete the code to run Lighthouse on a URL.

Astro

const result = await lighthouse('[1]');

Drag options to blanks, or click blank then click option'

Ahttps://example.com

Bastro.build

Chttp://localhost:3000

Dfile:///index.html

Attempts:

3 left

💡 Hint

Common Mistakes

Using a domain without protocol like 'astro.build'.

Using a file path instead of a URL.

You need to provide a full URL starting with https:// or http:// for Lighthouse to audit. https://example.com is a valid example.

3fill in blank

hard

Fix the error in the Lighthouse options object to enable performance category.

Astro

const options = { categories: { [1]: true } };

Drag options to blanks, or click blank then click option'

Aseo

Bperformance

Caccessibility

Dbest-practices

Attempts:

3 left

💡 Hint

Common Mistakes

Enabling the wrong category like SEO or accessibility.

Misspelling the category name.

The performance category must be set to true to audit performance metrics.

4fill in blank

hard

Fill both blanks to extract the performance score from Lighthouse results.

Astro

const score = result.lhr.[1].[2];

Drag options to blanks, or click blank then click option'

Acategories

Bscore

Caudits

Dperformance

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'audits' instead of 'categories' for the first blank.

Using 'score' instead of 'performance' for the second blank.

The performance score is found under result.lhr.categories.performance.

5fill in blank

hard

Fill all three blanks to create a summary object with performance score and URL.

Astro

const summary = { url: [1], score: result.lhr.categories.[2].[3] };

Drag options to blanks, or click blank then click option'

A'https://mysite.com'

Bperformance

Cscore

D'http://localhost:8080'

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around the URL string.

Using wrong category name or property for score.

The URL should be a string with quotes, here 'http://localhost:8080'. The score is under categories.performance.score.

Practice

1. What is the main purpose of using Lighthouse with an Astro site?

easy

A. To check and improve the site's performance and usability

B. To write new Astro components automatically

C. To deploy the Astro site to a server

D. To convert Astro code into plain HTML

Solution

1. Step 1: Understand Lighthouse's role

   Lighthouse is a tool designed to analyze websites and provide reports on performance, accessibility, SEO, and best practices.

2. Step 2: Relate to Astro site improvement

   Using Lighthouse on an Astro site helps find ways to improve speed and usability, making the site better for users.

3. Final Answer:

   To check and improve the site's performance and usability -> Option A

4. Quick Check:

   Lighthouse purpose = Performance & usability check [OK]

Hint: Lighthouse audits site quality, not code writing or deployment [OK]

Common Mistakes:

• Thinking Lighthouse writes code
• Confusing Lighthouse with deployment tools
• Assuming Lighthouse converts code formats

2. Which command correctly runs Lighthouse from the command line for the URL https://example.com?

easy

A. start lighthouse --url https://example.com

B. run lighthouse https://example.com

C. lighthouse https://example.com

D. lighthouse run https://example.com

Solution

1. Step 1: Recall Lighthouse CLI syntax

   The basic command to run Lighthouse is simply lighthouse followed by the URL.

2. Step 2: Match the correct syntax

   lighthouse https://example.com matches the correct syntax: lighthouse https://example.com. Other options add unnecessary words or flags.

3. Final Answer:

   lighthouse https://example.com -> Option C

4. Quick Check:

   Correct CLI syntax = lighthouse URL [OK]

Hint: Use just 'lighthouse' plus URL to run audit [OK]

Common Mistakes:

• Adding extra words like 'run' or 'start'
• Using incorrect flags or options
• Confusing command order

3. After running Lighthouse on your Astro site, you see a low score in the 'Performance' category. What is the most likely cause?

medium

A. The site is missing a favicon

B. The site uses too many Astro components

C. The site has no SEO metadata

D. The site has large images and slow loading scripts

Solution

1. Step 1: Understand what affects Performance score

   Performance issues usually come from slow loading resources like large images or heavy scripts.

2. Step 2: Eliminate unrelated options

   SEO metadata and favicon affect SEO or appearance, not performance. Number of Astro components alone doesn't cause low performance.

3. Final Answer:

   The site has large images and slow loading scripts -> Option D

4. Quick Check:

   Performance issues = large images or slow scripts [OK]

Hint: Performance drops mainly due to heavy resources [OK]

Common Mistakes:

• Confusing SEO issues with performance
• Blaming Astro components count directly
• Ignoring resource sizes

4. You ran Lighthouse but the report shows no data and an error message. What is the most likely mistake?

medium

A. You ran Lighthouse without specifying a URL

B. You ran Lighthouse on a local file without a server

C. You forgot to install Astro globally

D. You used an outdated version of Node.js

Solution

1. Step 1: Identify why Lighthouse shows no data

   Lighthouse needs a live URL to audit. Running it on a local file without a server means no data can be fetched.

2. Step 2: Check other options

   Not specifying a URL would cause a command error, not a no data report. Astro installation or Node.js version do not directly cause this error.

3. Final Answer:

   You ran Lighthouse on a local file without a server -> Option B

4. Quick Check:

   Lighthouse needs live URL, not local file [OK]

Hint: Always run Lighthouse on a live server URL, not local files [OK]

Common Mistakes:

• Running Lighthouse on local files without server
• Ignoring error messages about URL
• Assuming Astro install affects Lighthouse

5. You want to improve your Astro site's Lighthouse performance score. Which combination of actions is best?

hard

A. Optimize images, lazy-load components, and reduce JavaScript size

B. Add more Astro components and increase CSS animations

C. Remove all images and use only text content

D. Disable Lighthouse caching and run audits repeatedly

Solution

1. Step 1: Identify actions that improve performance

   Optimizing images reduces load time, lazy-loading defers offscreen content, and reducing JS size speeds up scripts.

2. Step 2: Evaluate other options

   Adding components or animations can slow performance. Removing all images is impractical. Disabling caching doesn't improve site speed.

3. Final Answer:

   Optimize images, lazy-load components, and reduce JavaScript size -> Option A

4. Quick Check:

   Best performance = optimize images + lazy-load + reduce JS [OK]

Hint: Focus on image size, lazy loading, and JS reduction [OK]

Common Mistakes:

• Thinking more components always help
• Removing images entirely
• Misunderstanding caching effects