v-for with index in Vue - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to loop over items and display each item.

Vue

<li v-for="(item, [1]) in items">{{ item }}</li>

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

Aindex

Bkey

Ci

Didx

Attempts:

3 left

💡 Hint

Common Mistakes

Using only one variable without parentheses when you want the index.

Using a variable name that is not descriptive.

The second variable in v-for is commonly named index to represent the current loop index.

2fill in blank

medium

Complete the code to display the index before each item in the list.

Vue

<li v-for="(item, [1]) in items">{{ [1] + 1 }}. {{ item }}</li>

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

Ai

Bkey

Cindex

Didx

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong variable name for the index.

Not adding 1 to start counting from 1.

The index variable is used to show the position of each item. Adding 1 makes it start from 1 instead of 0.

3fill in blank

hard

Fix the error in the code to correctly use v-for with index.

Vue

<li v-for="(item, [1]) in items">{{ item }} - {{ [1] }}</li>

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

Aindex

B(idx)

C(index)

Didx

Attempts:

3 left

💡 Hint

Common Mistakes

Not using parentheses around multiple variables.

Using a comma outside parentheses.

When using multiple variables in v-for, they must be wrapped in parentheses.

4fill in blank

hard

Fill both blanks to correctly bind a unique key using the index in v-for.

Vue

<li v-for="(item, [1]) in items" :key="[2]">{{ item }}</li>

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

Aindex

Bitem

Ditem.id

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names for the index and key.

Using the item itself as the key without a unique identifier.

The index variable is used in both the loop and as the unique key for each item.

5fill in blank

hard

Fill all three blanks to correctly display the index, item, and bind a unique key.

Vue

<li v-for="([1], [2]) in items" :key="[3]">{{ [2] + 1 }}. {{ [1] }}</li>

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

Aitem

Bindex

Ditem.id

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the order of item and index.

Using item.id as key when items don't have an id.

The loop uses (item, index), the key uses index, and the display shows index + 1 and the item.

Practice

1. What does the v-for directive do in Vue when used with a list?

easy

A. Creates a single element regardless of list size

B. Deletes items from the list

C. Sorts the list items alphabetically

D. Repeats an element for each item in the list

Solution

1. Step 1: Understand the purpose of v-for

   The v-for directive is designed to repeat an element for each item in a list or array.

2. Step 2: Compare options with this behavior

   Only Repeats an element for each item in the list describes repeating elements for each list item, which matches v-for usage.

3. Final Answer:

   Repeats an element for each item in the list -> Option D

4. Quick Check:

   v-for repeats elements [OK]

Hint: Remember: v-for loops over lists to repeat elements [OK]

Common Mistakes:

• Thinking v-for deletes or sorts items
• Confusing v-for with conditional rendering
• Assuming v-for creates only one element

2. Which of the following is the correct syntax to use v-for with an index in Vue?

easy

A. v-for="(item, index) in items"

B. v-for="item, index in items"

C. v-for="item in items, index"

D. v-for="items as item, index"

Solution

1. Step 1: Recall correct v-for syntax with index

   The correct syntax is v-for="(item, index) in items", where the item and index are inside parentheses.

2. Step 2: Check each option

   Only v-for="(item, index) in items" uses parentheses correctly and the right order: item then index.

3. Final Answer:

   v-for="(item, index) in items" -> Option A

4. Quick Check:

   Parentheses around item and index = v-for="(item, index) in items" [OK]

Hint: Use parentheses around item and index in v-for [OK]

Common Mistakes:

• Omitting parentheses around item and index
• Placing index after the list instead of inside parentheses
• Using commas outside parentheses

3. Given the Vue template snippet:

<ul>
  <li v-for="(fruit, i) in ['apple', 'banana', 'cherry']" :key="i">{{ i }} - {{ fruit }}</li>
</ul>

What will be the rendered list items?

medium

A. 1 - apple2 - banana3 - cherry

B. 0 - apple1 - banana2 - cherry

C. apple - 0banana - 1cherry - 2

D. applebananacherry

Solution

1. Step 1: Understand the loop and index

   The loop goes over the array ['apple', 'banana', 'cherry'] with index i starting at 0.

2. Step 2: Check the output format

   Each list item shows "{{ i }} - {{ fruit }}", so index then fruit name separated by a dash.

3. Final Answer:

   0 - apple
   1 - banana
   2 - cherry -> Option B

4. Quick Check:

   Index starts at 0, format is 'index - fruit' [OK]

Hint: Index in v-for starts at 0 by default [OK]

Common Mistakes:

• Assuming index starts at 1
• Swapping index and item in output
• Ignoring the :key binding

4. Identify the error in this Vue snippet:

<div v-for="item, index in items" :key="index">
  {{ index }}: {{ item }}
</div>

medium

A. Missing parentheses around item and index

B. Incorrect use of :key attribute

C. Using index instead of item in interpolation

D. v-for cannot be used on div elements

Solution

1. Step 1: Check v-for syntax

   The syntax for v-for with index requires parentheses: v-for="(item, index) in items".

2. Step 2: Analyze the given code

   The code uses v-for="item, index in items" without parentheses, which is invalid.

3. Final Answer:

   Missing parentheses around item and index -> Option A

4. Quick Check:

   Parentheses required for multiple variables in v-for [OK]

Hint: Always wrap item and index in parentheses in v-for [OK]

Common Mistakes:

• Omitting parentheses causes syntax error
• Misplacing :key attribute
• Thinking v-for can't be on div

5. You have a list of users with IDs and names:

users = [
  { id: 101, name: 'Alice' },
  { id: 102, name: 'Bob' },
  { id: 103, name: 'Carol' }
]

Which Vue template correctly uses v-for with index and sets a unique :key for each user?

hard

A. <div v-for="(user, i) in users" :key="i">{{ user.name }}</div>

B. <div v-for="user in users" :key="user.id">{{ user.name }}</div>

C. <div v-for="(user, index) in users" :key="user.id">{{ index }} - {{ user.name }}</div>

D. <div v-for="(user, index) in users" :key="index">{{ user.id }}: {{ user.name }}</div>

Solution

1. Step 1: Identify correct v-for syntax with index

   Options A, B, and D use (user, index) syntax correctly; C does not use index.

2. Step 2: Check for unique :key usage

   Keys should be unique and stable. Using user.id is best. <div v-for="(user, index) in users" :key="user.id">{{ index }} - {{ user.name }}</div> uses :key="user.id" with index, which is correct.

3. Step 3: Verify output format

   <div v-for="(user, index) in users" :key="user.id">{{ index }} - {{ user.name }}</div> shows index and user name, which matches the question requirement.

4. Final Answer:

   <div v-for="(user, index) in users" :key="user.id">{{ index }} - {{ user.name }}</div> -> Option C

5. Quick Check:

   Use (item, index) with unique :key from item [OK]

Hint: Use item ID for :key, index for display only [OK]

Common Mistakes:

• Using index as :key causing update issues
• Not using parentheses for item and index
• Ignoring unique keys requirement