HTML rendering with {@html} in Svelte - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to render raw HTML stored in the variable content.

Svelte

<div>[1] content</div>

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

A{@html}

B{content}

C{#html}

D{html}

Attempts:

3 left

💡 Hint

Common Mistakes

Using {content} renders HTML as plain text.

Using {#html} is incorrect syntax.

Using {html} is not recognized by Svelte.

Use {@html} to render raw HTML in Svelte.

2fill in blank

medium

Complete the code to safely render the variable htmlString as HTML inside a section.

Svelte

<section>[1] htmlString</section>

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

A{html}

B{htmlString}

C{@html}

D{#html}

Attempts:

3 left

💡 Hint

Common Mistakes

Using {htmlString} renders the HTML as plain text.

Using {#html} is not valid syntax.

Using {html} does not render HTML.

{@html} tells Svelte to render the string as HTML inside the element.

3fill in blank

hard

Fix the error in rendering the variable rawHtml as HTML inside a div.

Svelte

<div>[1] rawHtml</div>

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

A{html}

B{rawHtml}

C{#html}

D{@html}

Attempts:

3 left

💡 Hint

Common Mistakes

Using {rawHtml} renders HTML as text, not HTML.

Using {#html} is invalid syntax.

Using {html} does not render HTML.

Only {@html} correctly renders raw HTML strings in Svelte.

4fill in blank

hard

Fill both blanks to render htmlContent as HTML inside a section and add an ARIA label for accessibility.

Svelte

<section aria-label=[1]>[2] htmlContent</section>

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

A"Rich content"

B{@html}

C'Rich content'

D{htmlContent}

Attempts:

3 left

💡 Hint

Common Mistakes

Missing quotes around the ARIA label value.

Using {htmlContent} renders HTML as text.

Using {html} or {#html} is invalid.

Use a string with quotes for the ARIA label and {@html} to render HTML.

5fill in blank

hard

Fill all three blanks to render dynamicHtml safely, add an ARIA label, and use a main semantic element.

Svelte

<main aria-label=[1]>[2] dynamicHtml <footer>[3]</footer></main>

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

A"Main content"

B{@html}

C© 2024 My Site

D{dynamicHtml}

Attempts:

3 left

💡 Hint

Common Mistakes

Using {dynamicHtml} renders HTML as text.

Missing quotes around ARIA label.

Putting HTML rendering syntax in footer.

Use quotes for ARIA label, {@html} to render HTML, and plain text for footer content.

Practice

1. What does the {@html} tag do in a Svelte component?

easy

A. It escapes HTML tags and shows them as plain text.

B. It renders a string as actual HTML inside the component.

C. It creates a new HTML element dynamically.

D. It comments out HTML code so it is not rendered.

Solution

1. Step 1: Understand {@html} purpose

   The {@html} tag tells Svelte to treat the string as HTML, not plain text.

2. Step 2: Compare with normal rendering

   Normally, Svelte escapes HTML tags to show them as text, but {@html} renders them as real HTML.

3. Final Answer:

   It renders a string as actual HTML inside the component. -> Option B

4. Quick Check:

   {@html} = renders HTML [OK]

Hint: Remember {@html} outputs HTML, not plain text [OK]

Common Mistakes:

• Thinking {@html} escapes HTML instead of rendering it
• Confusing {@html} with creating new elements
• Assuming {@html} comments out code

2. Which of the following is the correct syntax to render HTML stored in a variable htmlContent inside a Svelte component?

easy

A. <div>{@html htmlContent}</div>

B. <div>{@html(htmlContent)}</div>

C. <div>{htmlContent}</div>

D. <div>{#html htmlContent}{/html}</div>

Solution

1. Step 1: Recall correct {@html} syntax

   The correct syntax is {@html variableName} without parentheses or block tags.

2. Step 2: Check each option

   <div>{htmlContent}</div> renders as plain text, B uses invalid parentheses, D uses wrong block syntax.

3. Final Answer:

   <div>{@html htmlContent}</div> -> Option A

4. Quick Check:

   Correct {@html} syntax = {@html variable} [OK]

Hint: Use {@html variable} without parentheses or blocks [OK]

Common Mistakes:

• Adding parentheses around variable in {@html}
• Using block syntax like {#html}{/html}
• Not using {@html} and rendering raw string

3. Given this Svelte code:

  <script>
    let htmlString = '<strong>Hello</strong> <em>World</em>';
  </script>

  <div>{@html htmlString}</div>

What will be the rendered output in the browser?

medium

A. Hello World (plain text, no formatting)

B. <strong>Hello</strong> <em>World</em> (raw text)

C. Hello World (formatted text)

D. An error occurs because of unsafe HTML

Solution

1. Step 1: Understand {@html} rendering

   {@html renders the string as HTML, so tags become real formatting.

2. Step 2: Analyze the string content

   The string contains <strong> and <em> tags, so output will be bold and italic text.

3. Final Answer:

   <strong>Hello</strong> <em>World</em> (formatted text) -> Option C

4. Quick Check:

   HTML string renders as formatted text [OK]

Hint: {@html} renders tags as formatting, not raw text [OK]

Common Mistakes:

• Expecting tags to show as text instead of formatting
• Assuming plain text output without tags
• Thinking unsafe HTML causes runtime error

4. What is the main problem with this Svelte code?

  <script>
    let unsafeHtml = '';
  </script>

  <div>{@html unsafeHtml}</div>

medium

A. It can run unsafe scripts and cause security issues (XSS).

B. Svelte automatically sanitizes the HTML, so no problem.

C. The image will not display because of invalid src attribute.

D. It will cause a syntax error because of quotes inside the string.

Solution

1. Step 1: Identify unsafe HTML usage

   The string contains an image with an onerror event that runs JavaScript.

2. Step 2: Understand {@html} risks

   {@html renders raw HTML, so malicious scripts can run causing XSS security issues.

3. Final Answer:

   It can run unsafe scripts and cause security issues (XSS). -> Option A

4. Quick Check:

   {@html with unsafe HTML = security risk [OK]

Hint: Never use {@html} with untrusted content [OK]

Common Mistakes:

• Thinking Svelte sanitizes HTML automatically
• Assuming syntax error due to quotes inside string
• Believing image won't display due to src

5. You want to display user-generated content that may contain HTML tags safely in your Svelte app. Which approach is best?

hard

A. Wrap the user content in a <pre> tag and use {@html}.

B. Escape the user content and render it normally without {@html}.

C. Use {@html} directly on the user content to render formatting.

D. Sanitize the user content to remove unsafe tags, then use {@html}.

Solution

1. Step 1: Understand risks of raw {@html}

   Using {@html} directly on user content risks XSS attacks if content is unsafe.

2. Step 2: Best practice for safe HTML rendering

   Sanitize user content to remove dangerous tags/scripts, then render with {@html} for formatting.

3. Final Answer:

   Sanitize the user content to remove unsafe tags, then use {@html}. -> Option D

4. Quick Check:

   Sanitize first, then {@html} = safe rendering [OK]

Hint: Always sanitize user HTML before {@html} rendering [OK]

Common Mistakes:

• Using {@html} directly on raw user input
• Escaping content but losing formatting
• Using <pre> which shows raw text, not formatted HTML