Else and else-if blocks in Svelte

Introduction

Else and else-if blocks let you show different things on the screen depending on conditions. They help your app react to different situations.

Showing a message if a user is logged in, and a different one if not.

Displaying different content based on a selected option in a form.

Showing a loading spinner while data is loading, then showing the data or an error message.

Changing the page content based on user choices or app state.

Syntax

Svelte

{#if condition}
  <!-- content if true -->
{:else if anotherCondition}
  <!-- content if anotherCondition is true -->
{:else}
  <!-- content if none of the above are true -->
{/if}

Use {:else if} to check another condition if the first is false.

Use {:else} to show content when all conditions are false.

Examples

Shows a welcome message if loggedIn is true, otherwise asks to log in.

Svelte

{#if loggedIn}
  <p>Welcome back!</p>
{:else}
  <p>Please log in.</p>
{/if}

Shows different grades based on the score value.

Svelte

{#if score >= 90}
  <p>Grade: A</p>
{:else if score >= 80}
  <p>Grade: B</p>
{:else}
  <p>Grade: C or below</p>
{/if}

Sample Program

This Svelte component shows a loading message first. After 2 seconds, it changes to a success message. If the status was anything else, it would show a failure message.

Svelte

<script>
  let status = 'loading';

  // Simulate status change after 2 seconds
  setTimeout(() => {
    status = 'success';
  }, 2000);
</script>

{#if status === 'loading'}
  <p>Loading data...</p>
{:else if status === 'success'}
  <p>Data loaded successfully!</p>
{:else}
  <p>Failed to load data.</p>
{/if}

Important Notes

Only one block inside {#if} ... {:else if} ... {:else} runs at a time.

You can have multiple {:else if} blocks to check many conditions.

Make sure to close the block with {/if}.

Summary

Use {#if} to start a condition block.

Use {:else if} to check another condition if the first is false.

Use {:else} to show content when all conditions fail.

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