v-model with checkboxes in Vue - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to bind the checkbox to the data property using v-model.

Vue

<template>
  <input type="checkbox" [1]="checked" />
</template>

<script setup>
import { ref } from 'vue'
const checked = ref(false)
</script>

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

Av-bind

Bv-if

Cv-model

Dv-for

Attempts:

3 left

💡 Hint

Common Mistakes

Using v-bind instead of v-model causes one-way binding only.

Using v-if or v-for here does not bind the checkbox state.

The v-model directive binds the checkbox's checked state to the checked data property, syncing user interaction with the data.

2fill in blank

medium

Complete the code to bind multiple checkboxes to an array using v-model.

Vue

<template>
  <input type="checkbox" value="apple" [1]="fruits" /> Apple
  <input type="checkbox" value="banana" [1]="fruits" /> Banana
</template>

<script setup>
import { ref } from 'vue'
const fruits = ref([])
</script>

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

Av-bind

Bv-if

Cv-show

Dv-model

Attempts:

3 left

💡 Hint

Common Mistakes

Using v-bind does not update the array on user clicks.

Using v-if or v-show does not bind the checkbox values.

Using v-model on checkboxes with a shared array allows multiple selections to be stored in the fruits array.

3fill in blank

hard

Fix the error in the code by completing the directive to correctly bind the checkbox group.

Vue

<template>
  <input type="checkbox" value="red" [1]="colors" /> Red
  <input type="checkbox" value="blue" [1]="colors" /> Blue
</template>

<script setup>
import { ref } from 'vue'
const colors = ref(['red'])
</script>

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

Av-model

Bv-bind

Cv-if

Dv-show

Attempts:

3 left

💡 Hint

Common Mistakes

Using v-bind causes the checkboxes not to update the array.

Using v-if or v-show does not bind the checkbox values.

The v-model directive correctly binds the checkbox group to the colors array, allowing multiple selections and initial values.

4fill in blank

hard

Fill both blanks to create a checkbox group bound to an array and display the selected items.

Vue

<template>
  <input type="checkbox" value="cat" [1]="pets" /> Cat
  <input type="checkbox" value="dog" [1]="pets" /> Dog
  <p>Selected pets: [2]</p>
</template>

<script setup>
import { ref } from 'vue'
const pets = ref([])
</script>

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

Av-model

Bpets.join(', ')

Cpets

Dv-bind

Attempts:

3 left

💡 Hint

Common Mistakes

Using v-bind instead of v-model prevents updating the array.

Displaying the array directly shows it as an object, not a readable list.

Use v-model to bind the checkboxes to the pets array. Display the selected pets as a comma-separated string using pets.join(', ').

5fill in blank

hard

Fill all three blanks to bind checkboxes to an array, display count, and disable a checkbox conditionally.

Vue

<template>
  <input type="checkbox" value="java" [1]="languages" :disabled="languages.length >= 2 && !languages.includes('java')" /> Java
  <input type="checkbox" value="python" [1]="languages" :disabled="languages.length >= 2 && !languages.includes('python')" /> Python
  <input type="checkbox" value="js" [1]="languages" :disabled="languages.length >= 2 && !languages.includes('js')" /> JavaScript
  <p>Selected count: [2]</p>
  <p>Selected languages: [3]</p>
</template>

<script setup>
import { ref } from 'vue'
const languages = ref([])
</script>

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

Av-model

Blanguages.length

Clanguages.join(', ')

Dv-bind

Attempts:

3 left

💡 Hint

Common Mistakes

Using v-bind disables two-way binding.

Displaying the array directly shows an object, not a readable list.

Not disabling checkboxes allows selecting more than two.

Use v-model to bind checkboxes to the languages array. Show the count with languages.length and list selected languages with languages.join(', '). The checkboxes disable when two are selected, preventing more selections.

Practice

1. What type of data should you use with v-model when binding to multiple checkboxes in Vue?

easy

A. A string representing the last selected checkbox

B. A boolean to represent true or false

C. An array to hold the selected values

D. A number counting how many checkboxes are checked

Solution

1. Step 1: Understand checkbox binding

   When multiple checkboxes are bound with v-model, Vue expects an array to store all selected values.

2. Step 2: Compare data types for checkboxes

   A boolean is used for single checkboxes, but for multiple checkboxes, an array collects all checked values.

3. Final Answer:

   An array to hold the selected values -> Option C

4. Quick Check:

   Multiple checkboxes = array [OK]

Hint: Multiple checkboxes always bind to an array [OK]

Common Mistakes:

• Using a boolean for multiple checkboxes
• Binding to a string instead of an array
• Expecting a number to track checked boxes

2. Which of the following is the correct syntax to bind a single checkbox with v-model in Vue?

easy

A. <input type='checkbox' v-model='checked' />

B. <input type='checkbox' :value='checked' />

C. <input type='checkbox' v-bind='checked' />

D. <input type='checkbox' v-model:value='checked' />

Solution

1. Step 1: Identify correct binding directive

   The v-model directive binds the checkbox's checked state to a data property.

2. Step 2: Check syntax correctness

   <input type='checkbox' v-model='checked' /> uses v-model='checked' which is the correct and simplest syntax for binding a single checkbox.

3. Final Answer:

   <input type='checkbox' v-model='checked' /> -> Option A

4. Quick Check:

   Single checkbox uses v-model='property' [OK]

Hint: Use v-model directly on checkbox for single binding [OK]

Common Mistakes:

• Using :value instead of v-model
• Using v-bind without specifying property
• Using v-model:value which is invalid

3. Given this Vue template code:

<template>
  <input type='checkbox' v-model='selected' value='apple' />
  <input type='checkbox' v-model='selected' value='banana' />
  <input type='checkbox' v-model='selected' value='cherry' />
  <p>Selected: {{ selected }}</p>
</template>

<script setup>
import { ref } from 'vue'
const selected = ref([])
</script>

What will be displayed after the user checks the boxes for "apple" and "cherry"?

medium

A. Selected: 'apple,cherry'

B. Selected: ['apple', 'cherry']

C. Selected: ['apple']

D. Selected: true

Solution

1. Step 1: Understand v-model with multiple checkboxes

   When multiple checkboxes share the same v-model bound to an array, Vue adds the checkbox's value to the array when checked.

2. Step 2: Check which boxes are selected

   User checked "apple" and "cherry", so the array contains ['apple', 'cherry'].

3. Final Answer:

   Selected: ['apple', 'cherry'] -> Option B

4. Quick Check:

   Checked boxes values collected in array [OK]

Hint: Multiple checkboxes with same v-model store values in array [OK]

Common Mistakes:

• Expecting a string instead of an array
• Thinking only last checked value is stored
• Confusing boolean with array for multiple checkboxes

4. What is wrong with this Vue checkbox binding?

<input type='checkbox' v-model='checked' value='yes' />

<script setup>
import { ref } from 'vue'
const checked = ref(false)
</script>

Why does checking the box not add 'yes' to checked?

medium

A. Because checked should be a string, not boolean

B. Because value attribute is missing

C. Because v-model cannot be used on checkboxes

D. Because checked is a boolean, not an array, so value is ignored

Solution

1. Step 1: Identify data type for v-model

   The variable checked is a boolean, so Vue treats the checkbox as a single toggle (true/false).

2. Step 2: Understand effect of value attribute

   When v-model is boolean, the value attribute is ignored; it only matters when binding to an array.

3. Final Answer:

   Because checked is a boolean, not an array, so value is ignored -> Option D

4. Quick Check:

   Boolean v-model ignores value attribute [OK]

Hint: Boolean v-model ignores value; use array for multiple values [OK]

Common Mistakes:

• Thinking value attribute always affects checkbox state
• Believing v-model can't be used on checkboxes
• Using string instead of boolean or array incorrectly

5. You want to create a group of checkboxes for selecting favorite fruits using v-model. The data property is favorites initialized as an empty array. Which code snippet correctly updates favorites when users check or uncheck fruits?

hard

A. <input type='checkbox' v-model='favorites' value='apple' />
<input type='checkbox' v-model='favorites' value='banana' />
<input type='checkbox' v-model='favorites' value='cherry' />

B. <input type='checkbox' v-model='favorites' :value='true' />
<input type='checkbox' v-model='favorites' :value='false' />

C. <input type='checkbox' v-model='favorites.apple' />
<input type='checkbox' v-model='favorites.banana' />

D. <input type='checkbox' v-model='favorites' value='true' />
<input type='checkbox' v-model='favorites' value='false' />

Solution

1. Step 1: Understand array binding for multiple checkboxes

   Binding multiple checkboxes to the same array with v-model and distinct value attributes collects checked values in the array.

2. Step 2: Evaluate each option's correctness

   <input type='checkbox' v-model='favorites' value='apple' /> <input type='checkbox' v-model='favorites' value='banana' /> <input type='checkbox' v-model='favorites' value='cherry' /> correctly uses v-model='favorites' with unique string values for each checkbox, so checked fruits are added or removed from the array.

3. Final Answer:

   <input type='checkbox' v-model='favorites' value='apple' /> <input type='checkbox' v-model='favorites' value='banana' /> <input type='checkbox' v-model='favorites' value='cherry' /> -> Option A

4. Quick Check:

   Multiple checkboxes + array + unique values = correct binding [OK]

Hint: Use array with unique values for multiple checkboxes [OK]

Common Mistakes:

• Using boolean values instead of unique strings
• Binding to object properties instead of array
• Using same value for all checkboxes