h function for creating vnodes in Vue - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a vnode for a <div> element using the h function.

Vue

const vnode = h([1]);

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

A'div'

B'span'

C'p'

D'button'

Attempts:

3 left

💡 Hint

Common Mistakes

Using a tag name that does not match the intended element.

Forgetting to put the tag name in quotes.

The h function creates a vnode for the specified HTML tag. Here, 'div' creates a

element vnode.

2fill in blank

medium

Complete the code to create a vnode for a <button> element with a click event handler using the h function.

Vue

const vnode = h('button', { [1]: () => alert('Clicked!') }, 'Click me');

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

AonClickHandler

BonClick

ConClickEvent

Donclick

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase like onclick instead of camelCase onClick.

Using incorrect property names like onClickEvent.

In Vue's h function, event listeners use camelCase with on prefix, so onClick is correct.

3fill in blank

hard

Fix the error in the code to create a vnode with children using the h function.

Vue

const vnode = h('ul', null, [[1]]);

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

Ah('li', { key: 1 }, 'Item 1')

Bh('li', 'Item 1')

Ch('li', { key: '1' }, 'Item 1')

Dh('li', { key: true }, 'Item 1')

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the key property.

Using a boolean as a key.

Keys should be unique and are typically strings. Using { key: '1' } is correct and helps Vue track list items.

4fill in blank

hard

Fill both blanks to create a vnode for a <p> element with a class and text content using the h function.

Vue

const vnode = h('p', { [1]: 'text-primary' }, [2]);

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

Aclass

Bstyle

C'Hello World!'

D'Welcome!'

Attempts:

3 left

💡 Hint

Common Mistakes

Using style instead of class for CSS classes.

Putting text inside the second argument instead of the third.

The class property sets the CSS class, and the third argument is the text content.

5fill in blank

hard

Fill all three blanks to create a vnode for a <section> with an id, inline style, and two child <p> elements using the h function.

Vue

const vnode = h('section', { [1]: 'main-section', [2]: { color: 'blue' } }, [h('p', null, [3]), h('p', null, 'Second paragraph')]);

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

Aid

Bstyle

C'First paragraph'

Dclass

Attempts:

3 left

💡 Hint

Common Mistakes

Using class instead of id for the id attribute.

Passing styles as a string instead of an object.

Forgetting to provide text content for the first

element.

The id sets the element's id, style sets inline styles as an object, and the third blank is the text for the first child paragraph.

Practice

1. What is the primary purpose of the h function in Vue?

easy

A. To define CSS styles for components

B. To directly manipulate the DOM elements

C. To fetch data from an API

D. To create virtual nodes representing elements or components

Solution

1. Step 1: Understand the role of h in Vue

   The h function is used to create virtual nodes (vnodes) which represent elements or components in Vue's virtual DOM.

2. Step 2: Differentiate from other functions

   It does not manipulate the real DOM directly, fetch data, or style components. Its main role is to build the virtual DOM structure.

3. Final Answer:

   To create virtual nodes representing elements or components -> Option D

4. Quick Check:

   h function = create virtual nodes [OK]

Hint: Remember: h builds virtual nodes, not real DOM [OK]

Common Mistakes:

• Confusing h with direct DOM manipulation
• Thinking h fetches data
• Assuming h styles components

2. Which of the following is the correct syntax to create a div element with the h function and a class of "container"?

easy

A. h('div', ['class', 'container'])

B. h('div', { class: 'container' })

C. h('div', 'class', 'container')

D. h('div', { 'className': 'container' })

Solution

1. Step 1: Recall the h function signature

   The h function takes the tag name as the first argument and an object of props as the second argument.

2. Step 2: Identify correct props syntax

   Vue uses class (not className) as the key for CSS classes in the props object.

3. Final Answer:

   h('div', { class: 'container' }) -> Option B

4. Quick Check:

   h(tag, props) with class key = A [OK]

Hint: Props are an object; use { class: 'name' } [OK]

Common Mistakes:

• Using 'className' instead of 'class'
• Passing class as separate string arguments
• Using array instead of object for props

3. What will be the rendered output of this Vue render function snippet?

return h('ul', null, [
  h('li', null, 'Apple'),
  h('li', null, 'Banana'),
  h('li', null, 'Cherry')
])

medium

A. AppleBananaCherry

B. AppleBananaCherry

C. AppleBananaCherry

D. Error: Children must be strings

Solution

1. Step 1: Understand the structure created by h

   The outer h creates a ul element with an array of li children nodes.

2. Step 2: Recognize the children rendering

   Each li vnode contains a string child representing the fruit name, so the final HTML is a list with three li items.

3. Final Answer:

   <ul><li>Apple</li><li>Banana</li><li>Cherry</li></ul> -> Option A

4. Quick Check:

   h with array children = nested elements [OK]

Hint: Array children create nested elements inside parent [OK]

Common Mistakes:

• Thinking children array concatenates text
• Expecting error for array children
• Missing the parent <ul> element

4. Identify the error in this usage of the h function:

return h('button', { onclick: () => alert('Clicked!') }, 'Click me')

medium

A. The event name should be lowercase: 'onclick'

B. The event handler should be passed as 'onClick' but as a string

C. The event handler should be passed as 'onClick' with capital C

D. The event handler should be passed as 'onClick' but inside an array

Solution

1. Step 1: Recall Vue event listener naming in h

   Vue expects event listeners in props to be prefixed with 'on' and camelCase event name, e.g., 'onClick'.

2. Step 2: Identify the incorrect casing

   The code uses 'onclick' with lowercase 'c', which Vue does not recognize as an event listener.

3. Final Answer:

   The event handler should be passed as 'onClick' with capital C -> Option C

4. Quick Check:

   Event props use camelCase event names [OK]

Hint: Use camelCase event names like 'onClick' in props [OK]

Common Mistakes:

• Using lowercase event names
• Passing event handler as string
• Wrapping handler in array unnecessarily

5. How would you use the h function to create a ul list from this array of fruits, but only include fruits with names longer than 5 characters?

const fruits = ['Apple', 'Banana', 'Fig', 'Cherry']

hard

A. h('ul', null, fruits.filter(f => f.length > 5).map(f => h('li', null, f)))

B. h('ul', null, fruits.map(f => f.length > 5 ? h('li', null, f) : f))

C. h('ul', null, fruits.map(f => h('li', null, f.length > 5)))

D. h('ul', null, fruits.filter(f => f.length > 5))

Solution

1. Step 1: Filter fruits by length

   Use filter to keep only fruits with names longer than 5 characters.

2. Step 2: Map filtered fruits to li vnodes

   Use map to convert each filtered fruit into an li vnode with the fruit name as child.

3. Step 3: Pass the array of li vnodes as children to ul

   This creates a ul with only the desired fruits as list items.

4. Final Answer:

   h('ul', null, fruits.filter(f => f.length > 5).map(f => h('li', null, f))) -> Option A

5. Quick Check:

   Filter then map to
6. nodes = A [OK]

Hint: Filter first, then map to <li> nodes inside h [OK]

Common Mistakes:

• Mapping without filtering includes unwanted items
• Passing booleans or nulls as children
• Passing raw strings array without wrapping in <li>