Each blocks ({#each}) in Svelte

Introduction

Each blocks let you show a list of items easily. They repeat a part of your page for every item in a list.

You want to show a list of names or things on your page.

You need to create a menu with many options from an array.

You want to display multiple cards or boxes with similar content.

You want to loop over data from a server and show it in your app.

Syntax

Svelte

{#each items as item}
  <!-- content using {item} -->
{/each}

You can use any variable name instead of item to represent each element.

You can also get the index of each item by adding , index after the item name.

Examples

This shows each fruit in the fruits list inside a paragraph.

Svelte

{#each fruits as fruit}
  <p>{fruit}</p>
{/each}

This shows each user's name with their number in the list.

Svelte

{#each users as user, i}
  <p>{i + 1}. {user.name}</p>
{/each}

This uses a key (number) to help Svelte track items when the list changes.

Svelte

{#each numbers as number (number)}
  <p>{number}</p>
{/each}

Sample Program

This Svelte component shows a list of colors with their position number. It uses an each block to repeat the list items.

Svelte

<script>
  let colors = ['Red', 'Green', 'Blue'];
</script>

<ul>
  {#each colors as color, index}
    <li>{index + 1}: {color}</li>
  {/each}
</ul>

Important Notes

Always close the each block with {/each}.

Using keys in each blocks helps Svelte update the list efficiently when items change.

You can nest each blocks inside each other for lists of lists.

Summary

Each blocks repeat content for every item in a list.

You can access the item and its index inside the block.

Keys help Svelte track list items for better updates.

Practice

1. What does the {#each} block do in Svelte?

easy

A. Creates a conditional statement to show or hide content

B. Repeats a block of HTML for each item in a list

C. Defines a reusable component

D. Declares a reactive variable

Solution

1. Step 1: Understand the purpose of {#each}

   The {#each} block is used to repeat content for every item in a list or array.

2. Step 2: Compare with other options

   Options A, C, and D describe other Svelte features, not list repetition.

3. Final Answer:

   Repeats a block of HTML for each item in a list -> Option B

4. Quick Check:

   {#each} = repeat list items [OK]

Hint: Remember: {#each} loops over lists [OK]

Common Mistakes:

• Confusing {#each} with {#if}
• Thinking it creates components
• Assuming it declares variables

2. Which of the following is the correct syntax to loop over an array items and display each item in Svelte?

easy

A. {#each items to item} <p>{item}</p> {/each}

B. {#each item in items} <p>{item}</p> {/each}

C. {#each items for item} <p>{item}</p> {/each}

D. {#each items as item} <p>{item}</p> {/each}

Solution

1. Step 1: Recall Svelte each block syntax

   The correct syntax is {#each array as item} to loop over an array.

2. Step 2: Check each option

   Only {#each items as item} <p>{item}</p> {/each} uses as correctly. Options A, B, and C use incorrect keywords.

3. Final Answer:

   {#each items as item} <p>{item}</p> {/each} -> Option D

4. Quick Check:

   Use as keyword in {#each} [OK]

Hint: Use 'as' keyword: {#each array as item} [OK]

Common Mistakes:

• Using 'in' instead of 'as'
• Using 'for' or 'to' keywords
• Missing the 'as' keyword

3. Given the code:

{`


  {#each fruits as fruit, i}
    
{i}: {fruit}
  {/each}
`}

What will be the rendered output inside the <ul>?

medium

A. 0: apple1: banana2: cherry

B. apple: 0banana: 1cherry: 2

C. 1: apple2: banana3: cherry

D. fruit: applefruit: bananafruit: cherry

Solution

1. Step 1: Understand the each block variables

   The loop uses fruit for the item and i for the index starting at 0.

2. Step 2: Match output format

   Each list item shows index, colon, then fruit name, so output is 0: apple, 1: banana, 2: cherry.

3. Final Answer:

   <li>0: apple</li><li>1: banana</li><li>2: cherry</li> -> Option A

4. Quick Check:

   Index starts at 0, item after colon [OK]

Hint: Index starts at 0 in {#each items as item, i} [OK]

Common Mistakes:

• Confusing index and item order
• Starting index at 1 instead of 0
• Using wrong variable names

4. What is wrong with this Svelte code snippet?

{`


  {#each numbers as number}
    
{num}
  {/each}
`}

medium

A. The variable inside the block should be 'number', not 'num'

B. The array 'numbers' is not defined

C. The each block syntax is incorrect

D. Missing closing {/each} tag

Solution

1. Step 1: Check variable names inside each block

   The loop defines number as the item, but inside the block it uses {num}, which is undefined.

2. Step 2: Verify other syntax parts

   The array is defined, the each block syntax and closing tag are correct.

3. Final Answer:

   The variable inside the block should be 'number', not 'num' -> Option A

4. Quick Check:

   Use same variable name inside each block [OK]

Hint: Use the exact loop variable name inside the block [OK]

Common Mistakes:

• Using a different variable name inside the block
• Forgetting to close the each block
• Misnaming the array variable

5. You want to render a list of users with unique IDs and update the list efficiently when users change. Which is the best way to use {#each} with keys in Svelte?

hard

A. {#each users as user (user.name)} <p>{user.name}</p> {/each}

B. {#each users as user} <p>{user.name}</p> {/each}

C. {#each users as user (user.id)} <p>{user.name}</p> {/each}

D. {#each users as user (index)} <p>{user.name}</p> {/each}

Solution

1. Step 1: Understand keys in each blocks

   Keys help Svelte track items uniquely for efficient updates. The key should be a unique, stable identifier like user.id.

2. Step 2: Evaluate options

   {#each users as user (user.id)} <p>{user.name}</p> {/each} uses user.id as key, which is best. {#each users as user} <p>{user.name}</p> {/each} has no key, less efficient. {#each users as user (user.name)} <p>{user.name}</p> {/each} uses user.name, which may not be unique. {#each users as user (index)} <p>{user.name}</p> {/each} uses index, which can cause issues when list changes.

3. Final Answer:

   {#each users as user (user.id)} <p>{user.name}</p> {/each} -> Option C

4. Quick Check:

   Use unique ID as key in each block [OK]

Hint: Use unique IDs as keys: {#each items as item (item.id)} [OK]

Common Mistakes:

• Not using keys at all
• Using non-unique keys like names
• Using index as key causing update bugs