Else and else-if blocks in Svelte - Mini Project: Build & Apply

Using else and else-if blocks in Svelte

📖 Scenario: You are building a simple Svelte component that shows a message based on the current hour of the day. This is like a digital greeting card that changes its message depending on the time.

🎯 Goal: Create a Svelte component that uses {#if}, {:else if}, and {:else} blocks to display different greetings for morning, afternoon, evening, and night.

📋 What You'll Learn

Create a variable hour with a number representing the current hour (0 to 23).

Create a variable morningStart set to 6 and afternoonStart set to 12.

Use {#if}, {:else if}, and {:else} blocks to show:

Good morning! if hour is between morningStart and afternoonStart - 1.

Good afternoon! if hour is between afternoonStart and 18.

Good evening! if hour is between 19 and 21.

Good night! for all other hours.

💡 Why This Matters

🌍 Real World

Time-based greetings are common in apps and websites to personalize user experience depending on the time of day.

💼 Career

Understanding conditional rendering in Svelte is essential for building interactive user interfaces that respond to data changes.

1

Set up the hour variable

Create a variable called hour and set it to 14 inside a <script> tag.

Svelte

  // Your code here

Hint

Use let hour = 14; inside the <script> tag.

2

Add morning and afternoon start variables

Inside the <script> tag, add two variables: morningStart set to 6 and afternoonStart set to 12.

Svelte

  let hour = 14;
  // Your code here

Hint

Declare morningStart and afternoonStart with the given values.

3

Add if, else if, and else blocks for greetings

Below the <script> tag, use Svelte's {#if}, {:else if}, and {:else} blocks to show these messages based on hour: Good morning! if hour is between morningStart and afternoonStart - 1, Good afternoon! if hour is between afternoonStart and 18, Good evening! if hour is between 19 and 21, and Good night! for all other hours.

Svelte

  let hour = 14;
  let morningStart = 6;
  let afternoonStart = 12;

Hint

Use Svelte's {#if}, {:else if}, and {:else} blocks with the exact conditions and messages.

4

Complete the Svelte component

Make sure the entire Svelte component includes the <script> tag with variables and the conditional blocks below it exactly as described.

Svelte

  let hour = 14;
  let morningStart = 6;
  let afternoonStart = 12;


{#if hour >= morningStart && hour Good morning!
{:else if hour >= afternoonStart && hour Good afternoon!
{:else if hour >= 19 && hour Good evening!
{:else}
  Good night!
{/if}

Hint

Review the full component to ensure all parts are included and correct.

Practice

1. In Svelte, which block is used to check a second condition if the first {#if} condition is false?

easy

A. {:else}

B. {#each}

C. {:else if}

D. {#await}

Solution

1. Step 1: Understand the purpose of {#if} and {:else if}

   The {#if} block checks the first condition. If it is false, {:else if} allows checking another condition.

2. Step 2: Identify the correct block for a second condition

   {:else if} is specifically designed to check additional conditions after the first fails.

3. Final Answer:

   {:else if} -> Option C

4. Quick Check:

   Second condition check = {:else if} [OK]

Hint: Use {:else if} to test another condition after {#if} fails [OK]

Common Mistakes:

• Using {:else} to check a condition instead of fallback
• Confusing {#each} with conditional blocks
• Trying to use {#await} for conditions

2. Which of the following is the correct syntax for an else-if block in Svelte?

easy

A. {:elseif condition}

B. {:else if condition}

C. {:else-if condition}

D. {:else if (condition)}

Solution

1. Step 1: Recall Svelte syntax for else-if

   Svelte uses {:else if} followed by the condition without parentheses.

2. Step 2: Compare options to correct syntax

   {:else if condition} matches the correct syntax exactly: {:else if condition}

3. Final Answer:

   {:else if condition} -> Option B

4. Quick Check:

   Correct else-if syntax = {:else if condition} [OK]

Hint: Remember: space between else and if, no parentheses [OK]

Common Mistakes:

• Writing {:elseif} as one word
• Adding parentheses around condition
• Using hyphen in else-if

3. What will be rendered by this Svelte code?

{`\n{#if score >= 90}\n  
Excellent
\n{:else if score >= 60}\n  
Good
\n{:else}\n  
Try again
\n{/if}`}

medium

A. Good

B. Try again

C. Excellent

D. No output

Solution

1. Step 1: Evaluate the first condition

   score is 75, which is not >= 90, so the first {#if} block is false.

2. Step 2: Evaluate the else-if condition

   score is 75, which is >= 60, so {:else if} block is true and renders <p>Good</p>.

3. Final Answer:

   <p>Good</p> -> Option A

4. Quick Check:

   score 75 triggers else-if block = Good [OK]

Hint: Check conditions top-down; first true block renders [OK]

Common Mistakes:

• Assuming all blocks render instead of only one
• Misreading the score value
• Confusing else-if with else

4. Identify the error in this Svelte code snippet:

{`{#if isActive}\n  
Active
\n{:else if}\n  
Inactive
\n{/if}`}

medium

A. Missing condition after {:else if}

B. Incorrect closing tag {/if}

C. Cannot use {:else if} after {#if}

D. Missing colon before else

Solution

1. Step 1: Check {:else if} syntax

   The {:else if} block requires a condition to follow it, but none is provided here.

2. Step 2: Confirm other parts are correct

   The {#if} and {/if} tags are correctly placed, and {:else if} is allowed after {#if}.

3. Final Answer:

   Missing condition after {:else if} -> Option A

4. Quick Check:

   {:else if} needs a condition [OK]

Hint: Always add a condition after {:else if} [OK]

Common Mistakes:

• Leaving {:else if} without condition
• Confusing {:else} with {:else if}
• Misplacing {/if} tag

5. Given this Svelte code:

{`\n{#if status === 'loading'}\n  
Loading...
\n{:else if status === 'success'}\n  
Data loaded
\n{:else if status === 'error'}\n  
Error occurred
\n{:else}\n  
Idle
\n{/if}`}

What will be displayed if status is an empty string?

hard

A. Loading...

B. Data loaded

C. Error occurred

D. Idle

Solution

1. Step 1: Check each condition against empty string

   status is '', so none of the conditions 'loading', 'success', or 'error' match.

2. Step 2: Use {:else} block as fallback

   Since no conditions match, the {:else} block runs, rendering <p>Idle</p>.

3. Final Answer:

   <p>Idle</p> -> Option D

4. Quick Check:

   Empty string triggers else block = Idle [OK]

Hint: If no conditions match, {:else} block runs [OK]

Common Mistakes:

• Assuming empty string matches a condition
• Forgetting {:else} fallback
• Mixing up else-if and else blocks