Prefetching and preloading in Astro - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to prefetch a page in Astro.

Astro

<a href="/about" [1]>About</a>

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

Aprefetch

Bpreload

Clazy

Ddefer

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'preload' instead of 'prefetch' on links.

Confusing 'lazy' loading with prefetching.

In Astro, adding prefetch to a link tells the browser to fetch the page in advance.

2fill in blank

medium

Complete the code to preload a stylesheet in Astro.

Astro

<link rel="[1]" href="/styles.css">

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

Apreload

Blazy

Cstylesheet

Dprefetch

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'prefetch' instead of 'preload' for stylesheets.

Using 'stylesheet' as the rel attribute to preload.

To preload a stylesheet, use rel="preload" with the appropriate as attribute (not shown here).

3fill in blank

hard

Fix the error in the prefetch link attribute.

Astro

<a href="/contact" rel="[1]">Contact</a>

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

Astylesheet

Bpreload

Cprefetch preload

Dprefetch

Attempts:

3 left

💡 Hint

Common Mistakes

Using multiple rel values like 'prefetch preload' together.

Using 'preload' instead of 'prefetch' on links.

The correct way to prefetch a page link is to use rel="prefetch". Combining 'prefetch preload' is invalid.

4fill in blank

hard

Fill both blanks to preload a font correctly.

Astro

<link rel="[1]" href="/fonts/myfont.woff2" as="[2]" type="font/woff2" crossorigin>

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

Apreload

Bprefetch

Cfont

Dscript

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'prefetch' instead of 'preload' for fonts.

Using 'script' as the as attribute for fonts.

Fonts should be preloaded with rel="preload" and as="font" to tell the browser the resource type.

5fill in blank

hard

Fill all three blanks to prefetch a script with correct attributes.

Astro

<link rel="[1]" href="/scripts/app.js" as="[2]" crossorigin=[3]>

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

Apreload

Bscript

C"anonymous"

Dprefetch

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'preload' instead of 'prefetch' for scripts.

Omitting crossorigin or using incorrect values.

To prefetch a script, use rel="prefetch", as="script", and set crossorigin="anonymous" for CORS.

Practice

1. What is the main purpose of prefetching in Astro?

easy

A. To remove unused resources from the page

B. To load resources immediately for current use

C. To load resources in the background before they are needed

D. To delay loading resources until user interaction

Solution

1. Step 1: Understand prefetching concept

   Prefetching means loading resources quietly in the background before the user needs them.

2. Step 2: Compare with other options

   Preloading loads immediately, delaying is opposite, and removing resources is unrelated.

3. Final Answer:

   To load resources in the background before they are needed -> Option C

4. Quick Check:

   Prefetching = background loading [OK]

Hint: Prefetching = load early but quietly in background [OK]

Common Mistakes:

• Confusing prefetching with preloading
• Thinking prefetching delays loading
• Assuming prefetching removes resources

2. Which is the correct way to add a prefetch link in Astro's <head>?

easy

A.

B.

C.

D.

Solution

1. Step 1: Identify correct rel attribute for prefetch

   Prefetch uses rel="prefetch" to hint browser to load resource in background.

2. Step 2: Check other options

   Preload uses rel="preload", but question asks for prefetch. rel="fetch" is invalid.

3. Final Answer:

   <link rel="prefetch" href="/script.js"> -> Option D

4. Quick Check:

   Prefetch link uses rel="prefetch" [OK]

Hint: Prefetch link uses rel="prefetch" exactly [OK]

Common Mistakes:

• Using preload instead of prefetch
• Missing the rel attribute
• Using invalid rel values like fetch

3. Given this Astro component snippet, what will happen?

<head>
  <link rel="preload" as="style" href="/styles.css" />
</head>
<body>
  <h1>Hello</h1>
</body>

medium

A. The styles.css file loads immediately to style the page quickly

B. The styles.css file loads in the background after page load

C. The styles.css file is ignored by the browser

D. The styles.css file loads only when user scrolls

Solution

1. Step 1: Understand preload with as="style"

   Preload with as="style" tells browser to load CSS immediately for fast styling.

2. Step 2: Compare with prefetch behavior

   Prefetch loads in background, but preload loads right away to speed up rendering.

3. Final Answer:

   The styles.css file loads immediately to style the page quickly -> Option A

4. Quick Check:

   Preload with as="style" = immediate CSS load [OK]

Hint: Preload with as="style" loads CSS immediately [OK]

Common Mistakes:

• Confusing preload with prefetch
• Thinking preload delays loading
• Ignoring the as attribute importance

4. Identify the error in this Astro prefetch usage:

<head>
  <link rel="prefetch" as="script" href="/app.js" />
</head>

medium

A. Prefetch should not use the 'as' attribute

B. The href attribute is missing

C. rel="prefetch" is invalid in Astro

D. The link tag must be inside the body

Solution

1. Step 1: Check prefetch attribute usage

   Prefetch links should not include the as attribute; it's only for preload.

2. Step 2: Validate other attributes and placement

   The href is present, rel="prefetch" is valid, and link tags belong in head, not body.

3. Final Answer:

   Prefetch should not use the 'as' attribute -> Option A

4. Quick Check:

   Prefetch without 'as' attribute [OK]

Hint: Prefetch links never use 'as' attribute [OK]

Common Mistakes:

• Adding 'as' attribute to prefetch
• Placing link tags inside body
• Confusing prefetch with preload

5. You want to optimize loading a large image that will be shown on the next page in Astro. Which combination is best?

hard

A. Use <link rel="preload" as="image" href="/large.jpg" /> on current page

B. Use <link rel="prefetch" href="/large.jpg" /> on current page and preload on next page

C. Use <link rel="prefetch" href="/large.jpg" as="image" /> on current page

D. Do not preload or prefetch; load image only when user clicks

Solution

1. Step 1: Understand prefetch for next page resources

   Prefetch loads resources in background for future use, ideal for next page images.

2. Step 2: Combine with preload on next page

   Preloading on next page ensures immediate display when user arrives, improving UX.

3. Step 3: Check invalid options

   Preload on current page wastes bandwidth if image not shown now; 'as' attribute invalid with prefetch; delaying load hurts UX.

4. Final Answer:

   Use <link rel="prefetch" href="/large.jpg" /> on current page and preload on next page -> Option B

5. Quick Check:

   Prefetch now + preload later = best for next page image [OK]

Hint: Prefetch for next page, preload on arrival for speed [OK]

Common Mistakes:

• Preloading large images too early wasting bandwidth
• Adding 'as' attribute to prefetch links
• Not prefetching resources needed soon