Declaring props with export let in Svelte - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a prop named name in a Svelte component.

Svelte

export [1] name;

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

Alet

Bvar

Cconst

Dfunction

Attempts:

3 left

💡 Hint

Common Mistakes

Using var or const instead of let.

Forgetting to use export keyword.

In Svelte, you declare props using export let. This makes name a property that can be passed from a parent component.

2fill in blank

medium

Complete the code to declare a prop named age with a default value of 30.

Svelte

export let age = [1];

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

A30

Bnull

C"30"

Dundefined

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string "30" instead of number 30.

Leaving the value undefined.

Assigning 30 as the default value means if no value is passed, age will be 30.

3fill in blank

hard

Fix the error in the code to properly declare a prop named title.

Svelte

export let [1] = 'Hello';

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

A1title

Btitle

CTitle

Dtitle!

Attempts:

3 left

💡 Hint

Common Mistakes

Starting variable names with uppercase letters or numbers.

Including special characters like exclamation marks.

Variable names must start with a letter or underscore and contain no special characters. title is valid.

4fill in blank

hard

Fill both blanks to declare two props: count with default 0 and enabled with default true.

Svelte

export let [1] = 0;
export let [2] = true;

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

Acount

Benable

Cenabled

Dcounter

Attempts:

3 left

💡 Hint

Common Mistakes

Using enable instead of enabled.

Using counter instead of count.

The props are named count and enabled. The defaults are 0 and true respectively.

5fill in blank

hard

Fill all three blanks to declare props firstName, lastName, and age with default values "John", "Doe", and 25 respectively.

Svelte

export let [1] = "John";
export let [2] = "Doe";
export let [3] = 25;

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

AfirstName

Bage

ClastName

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the order of prop names.

Using incorrect default values or types.

The props must be declared with the exact names and default values as specified.

Practice

1. What does export let do inside a Svelte component's <script> block?

easy

A. It creates a local variable that cannot be changed.

B. It imports a module from another file.

C. It declares a prop that can be set from outside the component.

D. It defines a function inside the component.

Solution

1. Step 1: Understand the role of export let

   In Svelte, export let declares a property (prop) that the parent component can pass in.

2. Step 2: Differentiate from other uses

   Unlike local variables or imports, export let specifically exposes variables as props for customization.

3. Final Answer:

   It declares a prop that can be set from outside the component. -> Option C

4. Quick Check:

   Props = export let [OK]

Hint: Remember: export let means external prop [OK]

Common Mistakes:

• Confusing export let with import statements
• Thinking export let creates constants
• Assuming export let defines functions

2. Which of the following is the correct syntax to declare a prop named title with a default value of "Hello" in Svelte?

easy

A. export let title = "Hello";

B. let export title = "Hello";

C. export const title = "Hello";

D. let title = export "Hello";

Solution

1. Step 1: Recall correct syntax for props

   In Svelte, props are declared with export let followed by the variable name and optional default value.

2. Step 2: Check each option

   export let title = "Hello"; matches the correct syntax: export let title = "Hello";. Others have wrong order or keywords.

3. Final Answer:

   export let title = "Hello"; -> Option A

4. Quick Check:

   export let + name + = default [OK]

Hint: Use 'export let' before variable name for props [OK]

Common Mistakes:

• Swapping 'let' and 'export' keywords
• Using 'const' instead of 'let' for props
• Placing export after variable name

3. Given this Svelte component code:

<script>
  export let count = 5;
</script>

<p>Count is {count}</p>

What will be displayed if the component is used as <MyComponent count={10} />?

medium

A. Count is 5

B. Count is 10

C. Count is undefined

D. Syntax error

Solution

1. Step 1: Understand default and passed props

   The component sets a default count of 5, but the parent passes 10, which overrides the default.

2. Step 2: Determine rendered output

   The displayed text uses the passed value 10, so it shows "Count is 10".

3. Final Answer:

   Count is 10 -> Option B

4. Quick Check:

   Passed prop overrides default [OK]

Hint: Passed props override defaults [OK]

Common Mistakes:

• Assuming default always shows ignoring passed value
• Thinking undefined appears if prop is passed
• Confusing syntax error with valid code

4. Identify the error in this Svelte component code:

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

<p>Hello {name}</p>

medium

A. You cannot assign a value to a prop inside the component after declaration.

B. Missing default value for the prop name.

C. The export keyword should be after let.

D. The <p> tag cannot use curly braces.

Solution

1. Step 1: Understand prop assignment rules

   Props declared with export let should not be reassigned inside the component; they come from outside.

2. Step 2: Check the code

   The code tries to assign name = "John" after declaration, which is not allowed and causes an error.

3. Final Answer:

   You cannot assign a value to a prop inside the component after declaration. -> Option A

4. Quick Check:

   Props are read-only inside component [OK]

Hint: Don't reassign props inside component [OK]

Common Mistakes:

• Trying to set default by assignment after export let
• Confusing export let order
• Misunderstanding template syntax

5. You want to create a Svelte component that accepts a prop items which is an array, but if no prop is passed, it should default to an empty array. Which code correctly declares this prop?

hard

A. export const items = [];

B. export let items;if (!items) items = [];

C. let items = [];

D. export let items = [];

Solution

1. Step 1: Set default value in prop declaration

   In Svelte, you can assign a default value directly when declaring a prop with export let.

2. Step 2: Evaluate options

   export let items = []; correctly declares items with default empty array. export let items;
if (!items) items = []; tries to assign after declaration, which is not allowed. let items = []; is local variable, not prop. export const items = []; uses const which is incorrect for props.

3. Final Answer:

   export let items = []; -> Option D

4. Quick Check:

   Default values go in export let declaration [OK]

Hint: Assign default value in export let line [OK]

Common Mistakes:

• Assigning default after declaration
• Using const instead of let for props
• Not exporting the variable