JavaScript expressions in templates in Vue - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to display the value of message inside the template.

Vue

<template>
  <p>{{ [1] }}</p>
</template>

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

Amsg

Bmessage

Ctext

Dcontent

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that is not defined in the component.

Forgetting to use double curly braces for interpolation.

The double curly braces {{ }} in Vue templates are used to display JavaScript expressions. Here, message is the correct variable to show.

2fill in blank

medium

Complete the code to show the length of the items array in the template.

Vue

<template>
  <p>Total items: {{ [1] }}</p>
</template>

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

Aitems.count

Bitems.size

Citems.length

Ditems.total

Attempts:

3 left

💡 Hint

Common Mistakes

Using count or size which are not valid array properties in JavaScript.

Trying to call length() as a function.

In JavaScript, arrays have a length property that gives the number of elements.

3fill in blank

hard

Fix the error in the template expression to correctly show the uppercase version of name.

Vue

<template>
  <p>{{ name.[1]() }}</p>
</template>

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

AtoUpperCase

Buppercase

CtoUppercase

DUpperCase

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect capitalization like toUppercase or uppercase.

Forgetting the parentheses to call the method.

The correct JavaScript string method to convert text to uppercase is toUpperCase() with a capital C.

4fill in blank

hard

Fill both blanks to create a computed property that returns the doubled value of count.

Vue

<script setup>
import { computed } from 'vue'
const count = ref(5)
const doubleCount = computed(() => count[1][2])
</script>

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

A*

B+

C2

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition instead of multiplication.

Using the variable name count again instead of a number.

To double a number, multiply it by 2 using the * operator and the number 2.

5fill in blank

hard

Fill all three blanks to create a template expression that shows the first item in items in uppercase.

Vue

<template>
  <p>{{ items[1] [2] [3]() }}</p>
</template>

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

A[0]

B.charAt

C.toUpperCase

D.slice

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to access the first item before calling string methods.

Using incorrect method names or missing parentheses.

To get the first item, use [0]. To get the first letter, use .slice(0,1) or .charAt(0). Then convert it to uppercase with .toUpperCase(). Here, .slice and .toUpperCase are used as methods.

Practice

1. In Vue templates, which syntax correctly inserts a JavaScript expression to display a variable named message?

easy

A. [[ message ]]

B. { message }

C. {{ message }}

D. ${ message }

Solution

1. Step 1: Recognize Vue interpolation syntax

   Vue uses double curly braces {{ }} to insert JavaScript expressions in templates.

2. Step 2: Match the correct syntax for variable display

   The correct way to show the value of message is {{ message }}.

3. Final Answer:

   <code>{{ message }}</code> -> Option C

4. Quick Check:

   Vue interpolation = {{ }} [OK]

Hint: Use double curly braces {{ }} to insert expressions [OK]

Common Mistakes:

• Using single curly braces or square brackets
• Trying to use template literals syntax inside templates
• Forgetting to use any braces

2. Which of the following is the correct way to write a simple math expression inside a Vue template to add 5 and 3?

easy

A. {{ 5 & 3 }}

B. {{ 5 + 3 }}

C. {{ add(5, 3) }}

D. {{ '5' + '3' }}

Solution

1. Step 1: Understand expression evaluation in Vue templates

   Vue evaluates JavaScript expressions inside {{ }} as normal JavaScript.

2. Step 2: Identify the correct math addition expression

   5 + 3 correctly adds numbers to get 8. {{ '5' + '3' }} concatenates strings, {{ add(5, 3) }} calls an undefined function, and {{ 5 & 3 }} uses bitwise AND.

3. Final Answer:

   <code>{{ 5 + 3 }}</code> -> Option B

4. Quick Check:

   Math addition uses + inside {{ }} [OK]

Hint: Use normal JavaScript math inside {{ }} [OK]

Common Mistakes:

• Using string quotes for numbers causing concatenation
• Calling undefined functions inside templates
• Using bitwise operators instead of arithmetic

3. Given the Vue data property count: 4, what will be displayed by this template snippet?

<div>{{ count * 2 }}</div>

medium

A. 8

B. count * 2

C. 4 * 2

D. undefined

Solution

1. Step 1: Evaluate the expression inside the template

   The expression count * 2 multiplies the value of count (which is 4) by 2.

2. Step 2: Calculate the result

   4 multiplied by 2 equals 8, so the template will display 8.

3. Final Answer:

   8 -> Option A

4. Quick Check:

   4 * 2 = 8 [OK]

Hint: Multiply variables directly inside {{ }} [OK]

Common Mistakes:

• Expecting the expression to print as text
• Confusing variable name with string
• Assuming undefined if variable is not reactive

4. What is wrong with this Vue template expression?

<div>{{ user.name.toUpperCase }}</div>

Assuming user.name is a string.

medium

A. toUpperCase is not a valid method

B. Cannot use functions inside templates

C. user.name is undefined

D. Missing parentheses to call the function

Solution

1. Step 1: Identify the method usage error

   toUpperCase is a function and must be called with parentheses ().

2. Step 2: Correct the expression

   The correct expression is user.name.toUpperCase() to get the uppercase string.

3. Final Answer:

   Missing parentheses to call the function -> Option D

4. Quick Check:

   Call methods with () inside {{ }} [OK]

Hint: Always add () when calling functions in templates [OK]

Common Mistakes:

• Forgetting parentheses on method calls
• Trying to use unsupported functions
• Assuming properties auto-call functions

5. You want to display a list of numbers doubled inside a Vue template using numbers = [1, 2, 3]. Which expression correctly creates a comma-separated string of doubled numbers?

hard

A. {{ numbers.map(n => n * 2).join(', ') }}

B. {{ numbers * 2 }}

C. {{ numbers.forEach(n => n * 2) }}

D. {{ numbers.map(n => n * 2) }}

Solution

1. Step 1: Understand array transformation in templates

   To double each number, use map with a function n => n * 2.

2. Step 2: Convert the array to a string

   Using join(', ') converts the array to a comma-separated string for display.

3. Final Answer:

   <code>{{ numbers.map(n => n * 2).join(', ') }}</code> -> Option A

4. Quick Check:

   Use map + join for array display [OK]

Hint: Use map() then join() to show transformed arrays [OK]

Common Mistakes:

• Trying to multiply array directly
• Using forEach which returns undefined
• Not joining array to string for display