First Svelte component - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a simple Svelte component that displays a greeting.

Svelte

<script>
  let name = "World";
</script>

<h1>Hello, [1]!</h1>

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

Ausername

BName

Cname

Dgreeting

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that was not declared.

Forgetting to use curly braces around the variable.

The variable name holds the greeting target. Using {name} inside the HTML displays its value.

2fill in blank

medium

Complete the code to bind the input value to the name variable.

Svelte

<script>
  let name = "";
</script>

<input type="text" [1]={name} />
<p>Hello, {name}!</p>

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

Abind:value

Bvalue

Cbind

Dmodel

Attempts:

3 left

💡 Hint

Common Mistakes

Using just value attribute which does not update the variable.

Using incorrect binding syntax like bind or model.

In Svelte, bind:value connects the input's value to the variable, updating it as the user types.

3fill in blank

hard

Fix the error in the component to correctly display the message only if name is not empty.

Svelte

<script>
  let name = "";
</script>

[1] (name) {
  <p>Hello, {name}!</p>
}

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

Aif

B{#if

C{#each

Dwhile

Attempts:

3 left

💡 Hint

Common Mistakes

Using plain JavaScript if without Svelte block syntax.

Using {#each} which is for loops, not conditions.

Svelte uses {#if} blocks to conditionally render content. The syntax is {#if condition} ... {/if}.

4fill in blank

hard

Fill both blanks to create a button that increments a counter and displays it.

Svelte

<script>
  let count = 0;
  function increment() {
    count [1] 1;
  }
</script>

<button on:click=[2]>Add 1</button>
<p>Count: {count}</p>

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

A+=

B-=

Cincrement

Ddecrement

Attempts:

3 left

💡 Hint

Common Mistakes

Using -= which subtracts instead of adds.

Using wrong function name or missing the event handler.

The operator += adds 1 to count. The button's click event calls the increment function.

5fill in blank

hard

Fill all three blanks to create a reactive statement that doubles the count and displays it.

Svelte

<script>
  let count = 0;
  $: [1] = [2] * 2;
</script>

<button on:click=[3]>() => count += 1</button>
<p>Double: {double}</p>

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

Adouble

Bcount

C() => count += 1

Dincrement

Attempts:

3 left

💡 Hint

Common Mistakes

Not using the reactive $: syntax.

Using wrong variable names or missing the arrow function syntax.

The reactive statement uses $: double = count * 2; to update double when count changes. The button increments count with an inline arrow function.

Practice

1. What is the main purpose of a Svelte component?

easy

A. To write backend server code

B. To combine HTML, CSS, and JavaScript in one file for UI parts

C. To create database schemas

D. To manage operating system processes

Solution

1. Step 1: Understand what Svelte components do

   Svelte components bundle HTML, CSS, and JavaScript to build user interfaces.

2. Step 2: Compare options with this purpose

   Only To combine HTML, CSS, and JavaScript in one file for UI parts describes combining these parts for UI, others are unrelated.

3. Final Answer:

   To combine HTML, CSS, and JavaScript in one file for UI parts -> Option B

4. Quick Check:

   Svelte components = UI parts combined [OK]

Hint: Remember Svelte bundles UI code in one file [OK]

Common Mistakes:

• Thinking Svelte is for backend code
• Confusing Svelte with database tools
• Assuming Svelte manages OS tasks

2. Which of the following is the correct way to define a simple Svelte component that displays "Hello World!"?

easy

A. Hello {name}!

B. Hello World

C. function Hello() { return 'Hello World'; }

D. Hello World

Solution

1. Step 1: Identify Svelte syntax for components

   Svelte uses <script> for logic and HTML with curly braces for variables.

2. Step 2: Check which option matches this pattern

   <script>export let name = 'World';</script><h1>Hello {name}!</h1> uses <script> and {name} interpolation correctly; others are plain HTML or JS functions.

3. Final Answer:

   <script>export let name = 'World';</script><h1>Hello {name}!</h1> -> Option A

4. Quick Check:

   Svelte uses <script> and { } for variables [OK]

Hint: Look for <script> and { } interpolation in Svelte [OK]

Common Mistakes:

• Using plain HTML without <script>
• Writing JS functions instead of Svelte syntax
• Including full HTML document tags inside component

3. Given this Svelte component code:

<script>
  let count = 0;
</script>
<button on:click={() => count++}>Clicked {count} times</button>

What will the button display after clicking it 3 times?

medium

A. Clicked 3 times

B. Clicked 0 times

C. Clicked count times

D. Clicked NaN times

Solution

1. Step 1: Understand the initial state and event

   Variable count starts at 0; clicking button runs count++ to increase by 1.

2. Step 2: Calculate count after 3 clicks

   After 3 clicks, count increments 3 times: 0 + 3 = 3.

3. Final Answer:

   Clicked 3 times -> Option A

4. Quick Check:

   count increments on click = 3 [OK]

Hint: Count increments by 1 each click [OK]

Common Mistakes:

• Thinking count resets on each click
• Confusing variable name with string literal
• Expecting no change without explicit render

4. What is wrong with this Svelte component code?

<script>
  let message = 'Hi';
</script>
<h1>{message</h1>

medium

A. Script tag should be outside the component

B. Variable message is not declared

C. Missing closing curly brace in {message}

D. Using <h1> tag is invalid in Svelte

Solution

1. Step 1: Check the template syntax

   The expression {message} must have matching braces; here the closing brace is missing.

2. Step 2: Verify other parts

   Variable is declared, <h1> is valid, and <script> is correctly placed.

3. Final Answer:

   Missing closing curly brace in {message} -> Option C

4. Quick Check:

   Curly braces must open and close properly [OK]

Hint: Check all { } pairs in template expressions [OK]

Common Mistakes:

• Forgetting to close curly braces
• Thinking HTML tags are invalid in Svelte
• Misplacing the <script> tag

5. You want to create a Svelte component that shows a greeting only if a user name is provided. Which code correctly implements this?

hard

A. Hello {user}!

B. Hello {user || 'Guest'}!

C. Hello {user}!

D. {#if user}Hello {user}!{/if}

Solution

1. Step 1: Understand conditional rendering in Svelte

   Svelte uses {#if condition} ... {/if} blocks to show content conditionally.

2. Step 2: Check which option uses this correctly

   <script>export let user = '';</script>{#if user}<p>Hello {user}!</p>{/if} uses {#if user} to show greeting only if user is not empty; others always show or lack condition.

3. Final Answer:

   <script>export let user = '';</script>{#if user}<p>Hello {user}!</p>{/if} -> Option D

4. Quick Check:

   Use {#if} for conditional display [OK]

Hint: Use {#if} block to show content conditionally [OK]

Common Mistakes:

• Not using {#if} for conditional display
• Always showing greeting even if user is empty
• Using JS ternary inside <p> without Svelte block