Named slots in Svelte - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What will this Svelte component render?

Consider the following Svelte component usage:

<Parent>
  <div slot="header">Header Content</div>
  <div slot="footer">Footer Content</div>
</Parent>

And the Parent.svelte component:

<slot name="header"/>
<slot/>
<slot name="footer"/>

What will be the rendered output?

Svelte

<slot name="header"/>
<slot/>
<slot name="footer"/>

A <div>Header Content</div><div>Footer Content</div>

B <div></div><div>Header Content</div><div>Footer Content</div>

C <div>Header Content</div><div>Footer Content</div><div></div>

D <div>Header Content</div><div></div><div>Footer Content</div>

💡 Hint

Remember that the default slot renders content without a slot attribute.

The Parent component has three slots: named 'header', default (unnamed), and named 'footer'. The usage provides content only for 'header' and 'footer' slots. The default slot is empty, so it renders nothing.

📝 Syntax

intermediate

Which option correctly defines a named slot in Svelte?

Choose the correct syntax to define a named slot called "sidebar" inside a Svelte component.

A &lt;slot slot="sidebar"/&gt;

B &lt;slot name={sidebar}&gt;&lt;/slot&gt;

C &lt;slot name="sidebar"/&gt;

D &lt;slot slotName="sidebar"/&gt;

💡 Hint

Named slots use the name attribute exactly.

The correct way to define a named slot is using <slot name="sidebar"/>. Other options use incorrect attribute names or syntax.

❓ state_output

advanced

What is the output when using fallback content in named slots?

Given this Parent.svelte component:

<slot name="title">Default Title</slot>
<slot name="content">Default Content</slot>

And this usage:

<Parent>
  <div slot="content">Custom Content</div>
</Parent>

What will be rendered?

Svelte

<slot name="title">Default Title</slot>
<slot name="content">Default Content</slot>

A Default TitleCustom Content

B Default TitleDefault Content

C Custom ContentDefault Title

D Custom ContentCustom Content

💡 Hint

Fallback content shows only if no slot content is provided for that slot.

The 'title' slot has no content provided, so it renders its fallback 'Default Title'. The 'content' slot has custom content, so it renders 'Custom Content'.

🔧 Debug

advanced

Why does this named slot content not render?

Consider this Parent.svelte component:

<slot name="main"/>

And this usage:

<Parent>
  <div slot="content">Hello</div>
</Parent>

Why does "Hello" not appear in the output?

Svelte

<slot name="main"/>

A The slot name in usage ('content') does not match the slot name in Parent ('main').

B The slot attribute must be on the Parent component, not the child elements.

C Named slots require a fallback content to render anything.

D Svelte does not support named slots with div elements.

💡 Hint

Check if the slot names match exactly.

The slot attribute in the usage is 'content', but the Parent component expects 'main'. Because they don't match, the content is not rendered in the named slot.

🧠 Conceptual

expert

How many named slots are rendered in this scenario?

Given a Svelte component with these slots:

<slot name="header"/>
<slot/>
<slot name="footer"/>

And usage:

<Component>
  <div slot="header">H</div>
  <div slot="footer">F</div>
  <div>D</div>
  <div slot="sidebar">S</div>
</Component>

How many slots will render content?

Svelte

<slot name="header"/>
<slot/>
<slot name="footer"/>

A 2

B 3

C 4

D 1

💡 Hint

Only content matching slot names or default slot renders.

The 'header' slot gets 'H', the default slot gets 'D', and the 'footer' slot gets 'F'. The 'sidebar' slot is unused because no matching slot exists in the component. So 3 slots render content.

Practice

1. What is the main purpose of named slots in Svelte components?

easy

A. To allow placing content into specific parts of a component

B. To define component styles globally

C. To handle component state changes

D. To import external JavaScript files

Solution

1. Step 1: Understand what slots do

   Slots let you insert content inside a component from outside.

2. Step 2: Identify the role of named slots

   Named slots let you put content into specific places inside the component, not just one default spot.

3. Final Answer:

   To allow placing content into specific parts of a component -> Option A

4. Quick Check:

   Named slots = specific content placement [OK]

Hint: Named slots = content in specific component areas [OK]

Common Mistakes:

• Confusing slots with styling or state
• Thinking slots import files
• Assuming slots handle events

2. Which of the following is the correct syntax to define a named slot called header inside a Svelte component?

easy

A.

B.

C.

D.

Solution

1. Step 1: Recall slot syntax in Svelte

   Svelte uses the <slot> tag with a name attribute to define named slots.

2. Step 2: Match correct attribute

   The attribute to name a slot is name, not id or custom tags.

3. Final Answer:

   <slot name="header"></slot> -> Option D

4. Quick Check:

   Named slot syntax = <slot name="..."> [OK]

Hint: Named slots use syntax [OK]

Common Mistakes:

• Using id instead of name attribute
• Using custom tags instead of <slot>
• Omitting the name attribute

3. Given this Svelte component usage:

<MyComponent>
  <div slot="title">Welcome</div>
  <div slot="footer">Goodbye</div>
</MyComponent>

And inside MyComponent.svelte you have:

<slot name="title">Default Title</slot>
<slot name="footer">Default Footer</slot>

What will be rendered in the browser?

medium

A. Default Title and Default Footer ignoring the passed content

B. Only Welcome is shown, Goodbye is ignored

C. Welcome and Goodbye in their respective slot positions

D. An error occurs because slots are not used correctly

Solution

1. Step 1: Understand slot filling

   Content with slot="title" fills the named slot "title" in the component.

2. Step 2: Match passed content to slots

   The <div slot="title">Welcome</div> replaces the default title slot content, same for footer.

3. Final Answer:

   Welcome and Goodbye in their respective slot positions -> Option C

4. Quick Check:

   Named slots filled = passed content shown [OK]

Hint: Content with slot="name" replaces default slot content [OK]

Common Mistakes:

• Thinking default slot content always shows
• Assuming only default slot works
• Confusing slot attribute usage

4. What is wrong with this usage of named slots?

<MyComponent>
  <div slot="header">Hello</div>
  <div slot="footer">Bye</div>
  <div slot="header">Again</div>
</MyComponent>

Assuming MyComponent defines named slots header and footer.

medium

A. Slots must be direct children of the component, so this is invalid

B. Multiple elements use the same slot name 'header', causing only the last to render

C. Slot names must be unique and cannot be reused in the same component usage

D. There is no error; all content will render in the header slot

Solution

1. Step 1: Check multiple slot usage

   When multiple elements use the same slot name, only the last one is rendered in that slot.

2. Step 2: Understand slot content replacement

   The first header content is replaced by the second because slots accept one content block per name.

3. Final Answer:

   Multiple elements use the same slot name 'header', causing only the last to render -> Option B

4. Quick Check:

   Duplicate slot names = last content wins [OK]

Hint: Only one content block per named slot is rendered [OK]

Common Mistakes:

• Thinking all duplicates render together
• Believing slot names must be unique globally
• Assuming nested slots behave differently

5. You want to create a Svelte component Card with named slots for header, content, and footer. You also want to provide default content for each slot if none is passed. Which code snippet correctly implements this?

hard

A. Default Header
Default Content
Default Footer

B. Default Header
Default Content
Default Footer

C.

D. Default Header
Default Content
Default Footer

Solution

1. Step 1: Use correct named slot syntax with default content

   Named slots require name attribute and default content inside the slot tags.

2. Step 2: Verify all slots have names and defaults

   Default Header Default Content Default Footer correctly names all slots and provides default text inside each slot tag.

3. Final Answer:

   <slot name="header">Default Header</slot> <slot name="content">Default Content</slot> <slot name="footer">Default Footer</slot> -> Option A

4. Quick Check:

   Named slots with defaults = <slot name="...">default</slot> [OK]

Hint: Named slots need name attribute and default content inside [OK]

Common Mistakes:

• Omitting name attribute
• Using slot attribute without value
• Mixing default slot with named slots incorrectly