v-model with text inputs in Vue - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the rendered output after typing?

Consider this Vue component using v-model on a text input. What will be displayed below the input after the user types 'hello'?

Vue

<template>
  <input v-model="message" type="text" aria-label="Message input" />
  <p>You typed: {{ message }}</p>
</template>

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

A You typed: {{ message }}

B You typed:

C You typed: hello

D You typed: undefined

💡 Hint

Remember that v-model binds the input value to the variable reactively.

When the user types 'hello', the message variable updates reactively because of v-model. The paragraph shows the current value of message, so it displays 'You typed: hello'.

📝 Syntax

intermediate

Which option correctly binds a text input with v-model?

Which of the following Vue template snippets correctly uses v-model to bind a text input to a variable named username?

A <input v-model="username" type="text" />

B <input v-model:username="text" />

C <input v-bind:value="username" />

D <input :value="username" v-model="username" />

💡 Hint

v-model is a directive that binds the input's value and listens for changes automatically.

Option A correctly uses v-model="username" to bind the input's value to the username variable. Option A mixes :value and v-model which is redundant and can cause issues. Option A only binds the value but does not listen for changes. Option A uses invalid syntax.

❓ state_output

advanced

What is the value of message after input event?

Given this Vue component, what will be the value of message after the user types 'Vue' in the input?

Vue

<template>
  <input v-model="message" type="text" aria-label="Message input" />
</template>

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

A undefined

B "vue"

C ""

D "Vue"

💡 Hint

The input updates the variable exactly as typed.

The v-model directive binds the input's value to the message variable reactively. When the user types 'Vue', message becomes 'Vue' exactly.

🔧 Debug

advanced

Why does this v-model binding not update the variable?

Look at this Vue component code. The input does not update the text variable when typing. What is the cause?

Vue

<template>
  <input v-model="text" type="text" />
  <p>{{ text }}</p>
</template>

<script setup>
let text = ''
</script>

A The variable 'text' is not reactive because it is declared with 'let' instead of 'ref'.

B The input is missing the 'name' attribute required for v-model.

C The template must use 'v-bind' instead of 'v-model' for text inputs.

D The 'text' variable should be declared inside the template.

💡 Hint

Check how Vue tracks reactive data in script setup.

In Vue 3 with script setup, variables must be reactive to update the UI. Declaring text with let creates a normal variable, not reactive. Using ref('') makes it reactive and updates the UI when changed.

🧠 Conceptual

expert

What happens if you use v-model with a computed property without setter?

In Vue 3, if you bind a text input with v-model to a computed property that only has a getter (no setter), what will happen when the user types in the input?

Vue

<template>
  <input v-model="fullName" type="text" />
</template>

<script setup>
import { computed, ref } from 'vue'
const firstName = ref('John')
const lastName = ref('Doe')
const fullName = computed(() => `${firstName.value} ${lastName.value}`)
</script>

A The input will update normally and change the computed property value.

B Typing in the input will cause a runtime error because the computed property has no setter.

C The input will be read-only and not allow typing.

D The input will update but changes will be lost immediately.

💡 Hint

Think about how v-model tries to update the bound variable on input.

A computed property without a setter is read-only. v-model tries to update the value on input, but since there is no setter, Vue throws a runtime error indicating the computed property is read-only.

Practice

1. What does v-model do when used on a text input in Vue?

easy

A. It listens for clicks on the input but does not update the value.

B. It only sets the initial value of the input but does not update data.

C. It creates a two-way binding between the input and a data property.

D. It disables the input field from user interaction.

Solution

1. Step 1: Understand v-model purpose

   v-model connects the input's value with a Vue data property, syncing changes both ways.

2. Step 2: Compare options with v-model behavior

   Only It creates a two-way binding between the input and a data property. describes this two-way binding correctly; others describe incorrect or unrelated behaviors.

3. Final Answer:

   It creates a two-way binding between the input and a data property. -> Option C

4. Quick Check:

   v-model = two-way binding [OK]

Hint: Remember: v-model syncs input and data both ways [OK]

Common Mistakes:

• Thinking v-model only sets initial value
• Confusing v-model with event listeners
• Assuming v-model disables input

2. Which of the following is the correct syntax to bind a text input to a data property username using v-model?

easy

A.

B.

C.

D.

Solution

1. Step 1: Identify correct v-model syntax

   The correct syntax uses v-model="username" on the input element.

2. Step 2: Check input type and binding

   <input v-model="username" type="text" /> uses correct syntax and input type text. <input :v-model="username" type="text" /> incorrectly uses colon binding. <input v-bind:model="username" type="text" /> misuses v-bind. <input v-model='username' type='checkbox' /> uses checkbox type, not text.

3. Final Answer:

   <input v-model="username" type="text" /> -> Option A

4. Quick Check:

   Correct v-model syntax = [OK]

Hint: Use v-model="property" without colon for text inputs [OK]

Common Mistakes:

• Adding colon before v-model
• Using v-bind:model instead of v-model
• Mismatching input type with v-model usage

3. Given this Vue component code:

const app = Vue.createApp({
  data() {
    return { message: 'Hello' };
  }
});

// Template:
// <input v-model="message" type="text" />
// <p>{{ message }}</p>

What will be displayed in the paragraph after the user types "Hi Vue" in the input?

medium

A. Hello

B. {{ message }}

C. An empty string

D. Hi Vue

Solution

1. Step 1: Understand v-model effect on data

   Typing in the input updates the message data property immediately due to two-way binding.

2. Step 2: Check paragraph binding

   The paragraph displays {{ message }}, so it shows the updated value typed by the user.

3. Final Answer:

   Hi Vue -> Option D

4. Quick Check:

   Input changes update message = displayed text [OK]

Hint: v-model updates data instantly, reflected in template [OK]

Common Mistakes:

• Thinking paragraph shows initial value only
• Confusing mustache syntax as literal text
• Assuming input does not update data

4. What is wrong with this Vue template snippet?

<input v-model="userName" type="text" />
<p>User: {{ username }}</p>

Why does the paragraph not update when typing in the input?

medium

A. v-model cannot be used on text inputs.

B. The data property is named differently from the template binding.

C. The input type should be "password" for v-model to work.

D. Must use v-bind instead of v-model for inputs.

Solution

1. Step 1: Compare data property and template usage

   The input uses v-model="userName" but paragraph uses {{ username }} with different casing.

2. Step 2: Understand Vue is case-sensitive

   Vue treats userName and username as different properties, so paragraph does not update.

3. Final Answer:

   The data property is named differently from the template binding. -> Option B

4. Quick Check:

   Case mismatch breaks binding = The data property is named differently from the template binding. [OK]

Hint: Check exact spelling and casing of data and template names [OK]

Common Mistakes:

• Assuming v-model doesn't work on text inputs
• Thinking input type affects v-model binding
• Confusing v-bind and v-model usage

5. You want to create a form with two text inputs bound to firstName and lastName using v-model. You also want to display the full name live as the user types. Which Vue template snippet correctly achieves this?

hard

A.

Full Name: {{ firstName + ' ' + lastName }}

B.

Full Name: {{ firstName & lastName }}

C.

Full Name: {{ firstName.concat(lastName) }}

D.

Full Name: {{ firstName + lastName }}

Solution

1. Step 1: Check how full name is constructed

   <input v-model="firstName" type="text" /> <input v-model="lastName" type="text" /> <p>Full Name: {{ firstName + ' ' + lastName }}</p> concatenates firstName and lastName with a space, showing a proper full name.

2. Step 2: Analyze other options for correctness

   <input v-model="firstName" type="text" /> <input v-model="lastName" type="text" /> <p>Full Name: {{ firstName & lastName }}</p> uses & which is invalid in JS expressions. <input v-model="firstName" type="text" /> <input v-model="lastName" type="text" /> <p>Full Name: {{ firstName.concat(lastName) }}</p> uses concat without space, so names join without space. <input v-model="firstName" type="text" /> <input v-model="lastName" type="text" /> <p>Full Name: {{ firstName + lastName }}</p> concatenates without space, so names run together.

3. Final Answer:

   <input v-model="firstName" type="text" /> <input v-model="lastName" type="text" /> <p>Full Name: {{ firstName + ' ' + lastName }}</p> -> Option A

4. Quick Check:

   Use + with space to join strings in template [OK]

Hint: Use + ' ' + to join strings with space in mustache [OK]

Common Mistakes:

• Using & instead of + for string join
• Forgetting space between names
• Using concat without space