Peer modifier (sibling state reaction) in Tailwind - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to change the text color of the sibling <p> when the checkbox is checked.

Tailwind

<input type="checkbox" id="toggle" class="peer" />
<p class="[1]">This text changes color when checkbox is checked.</p>

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

Ahover:text-blue-500

Bchecked:text-blue-500

Cfocus:text-blue-500

Dpeer-checked:text-blue-500

Attempts:

3 left

💡 Hint

Common Mistakes

Using checked: instead of peer-checked:

Forgetting to add the peer class to the checkbox

The peer-checked: modifier applies styles to siblings when the peer element (checkbox) is checked.

2fill in blank

medium

Complete the code to make the sibling <div> visible only when the checkbox is checked.

Tailwind

<input type="checkbox" id="show" class="peer" />
<div class="hidden [1]">Visible when checked</div>

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

Apeer-hover:block

Bchecked:block

Cpeer-checked:block

Dfocus:block

Attempts:

3 left

💡 Hint

Common Mistakes

Using checked:block which does not affect siblings

Not setting the initial state to hidden

The peer-checked:block class makes the sibling div display as block when the checkbox is checked.

3fill in blank

hard

Fix the error in the code to change the sibling <span> text to red when the checkbox is checked.

Tailwind

<input type="checkbox" id="check" class="peer" />
<span class="[1]">Change my color</span>

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

Apeer-checked:text-red-600

Bfocus:text-red-600

Chover:text-red-600

Dchecked:text-red-600

Attempts:

3 left

💡 Hint

Common Mistakes

Using checked: which does not affect siblings

Using hover: or focus: which are unrelated here

Only peer-checked: applies styles to sibling elements based on the peer's checked state.

4fill in blank

hard

Fill both blanks to make the sibling <div> background green and text white when the checkbox is checked.

Tailwind

<input type="checkbox" id="bg-toggle" class="peer" />
<div class="[1] [2]">Styled on check</div>

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

Apeer-checked:bg-green-500

Bbg-gray-200

Cpeer-checked:text-white

Dtext-black

Attempts:

3 left

💡 Hint

Common Mistakes

Using checked: instead of peer-checked:

Forgetting to style both background and text color

peer-checked:bg-green-500 changes background and peer-checked:text-white changes text color when checkbox is checked.

5fill in blank

hard

Fill all three blanks to make the sibling <button> scale up, change background, and show shadow when the checkbox is checked.

Tailwind

<input type="checkbox" id="scale-toggle" class="peer" />
<button class="transform transition [1] [2] [3]">Hover me</button>

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

Apeer-checked:scale-110

Bpeer-checked:bg-purple-600

Cpeer-checked:shadow-lg

Dhover:scale-110

Attempts:

3 left

💡 Hint

Common Mistakes

Using hover: instead of peer-checked:

Missing transform class which is needed for scaling

Using peer-checked: modifiers applies scale, background color, and shadow to the button when the checkbox is checked.

Practice

1. What does the peer modifier in Tailwind CSS allow you to do?

easy

A. Add margin to an element when it is focused.

B. Style sibling elements based on the state of the element with peer.

C. Change the color of the element itself on hover.

D. Create animations on the element when clicked.

Solution

1. Step 1: Understand the role of peer

   The peer modifier is used on an element to mark it as a reference for sibling elements.

2. Step 2: Recognize sibling styling with peer-*

   Siblings can then use peer-* classes to change their style based on the peer element's state.

3. Final Answer:

   Style sibling elements based on the state of the element with peer. -> Option B

4. Quick Check:

   Peer modifier = sibling state styling [OK]

Hint: Peer lets siblings react to one element's state [OK]

Common Mistakes:

• Thinking peer styles the element itself
• Confusing peer with hover or focus on the same element
• Assuming peer adds animations automatically

2. Which of the following is the correct way to use the peer modifier in Tailwind CSS?

easy

A. <input type='checkbox' class='peer' /><label class='peer-checked:text-blue-500'>Check me</label>

B. <input type='checkbox' class='peer-checked' /><label class='peer:text-blue-500'>Check me</label>

C. <input type='checkbox' class='checked-peer' /><label class='text-blue-500'>Check me</label>

D. <input type='checkbox' class='peer' /><label class='checked-peer:text-blue-500'>Check me</label>

Solution

1. Step 1: Identify correct usage of peer on the input

   The element that changes state (checkbox) must have the class peer.

2. Step 2: Use peer-checked on sibling label

   The sibling uses peer-checked: prefix to style based on the checkbox state.

3. Final Answer:

   <input type='checkbox' class='peer' /><label class='peer-checked:text-blue-500'>Check me</label> -> Option A

4. Quick Check:

   Peer on input, peer-checked on sibling [OK]

Hint: Put peer on state element, peer-* on siblings [OK]

Common Mistakes:

• Using peer-checked on the input instead of sibling
• Mixing up class names like checked-peer
• Not adding peer class to the element changing state

3. Given this HTML snippet, what color will the <span> text be when the checkbox is checked?

<input type='checkbox' class='peer' id='toggle' />
<span class='peer-checked:text-green-600'>Status</span>

medium

A. The text will be blue when checked.

B. The text will be red when checked.

C. The text will be green (#16a34a) when checked.

D. The text color will not change on check.

Solution

1. Step 1: Check the peer class on checkbox

   The checkbox has class peer, so siblings can react to its state.

2. Step 2: Analyze the sibling span's class

   The span uses peer-checked:text-green-600, so when checkbox is checked, text color changes to green.

3. Final Answer:

   The text will be green (#16a34a) when checked. -> Option C

4. Quick Check:

   peer-checked:text-green-600 means green text on check [OK]

Hint: peer-checked changes sibling style on checked state [OK]

Common Mistakes:

• Assuming text changes color without peer class
• Confusing green-600 with red or blue
• Ignoring that peer must be on the input

4. Why does this code NOT change the sibling paragraph's text color when the checkbox is checked?

<input type='checkbox' id='check' class='checked' />
<p class='peer-checked:text-red-500'>Warning</p>

medium

A. Because the 'checked' class on input does not trigger sibling styles; only 'peer' does.

B. Because the input has both 'checked' and 'peer' classes, which is invalid.

C. Because the 'checked' class on input is incorrect; it should be 'peer-checked'.

D. Because the 'peer' class must be alone without other classes.

Solution

1. Step 1: Understand the role of 'peer' and 'checked'

   The 'peer' class marks the element for sibling state detection. 'checked' is not a valid Tailwind class for inputs.

2. Step 2: Identify why sibling styles don't apply

   The sibling uses 'peer-checked', which reacts to the input's checked state only if the input has 'peer' class. 'checked' class on input does nothing.

3. Final Answer:

   Because the 'checked' class on input does not trigger sibling styles; only 'peer' does. -> Option A

4. Quick Check:

   Only 'peer' triggers sibling state styles [OK]

Hint: Only 'peer' triggers sibling styles, not 'checked' class [OK]

Common Mistakes:

• Thinking 'checked' class triggers styles
• Assuming multiple classes break peer
• Confusing 'checked' class with input state

5. You want a button's background to turn blue only when a checkbox sibling is focused or checked. Which Tailwind classes correctly achieve this?

<input type='checkbox' class='peer' />
<button class='???'>Submit</button>

hard

A. peer-checked:bg-blue-600 focus-within:bg-blue-600

B. checked:bg-blue-600 focus:bg-blue-600

C. peer:bg-blue-600 peer-checked:bg-blue-600

D. peer-checked:bg-blue-600 peer-focus:bg-blue-600

Solution

1. Step 1: Identify the states to react to on the checkbox

   The checkbox can be checked or focused. We want the button to change background in both cases.

2. Step 2: Use correct peer modifiers on the button

   Use peer-checked:bg-blue-600 for checked state and peer-focus:bg-blue-600 for focus state on the sibling button.

3. Final Answer:

   peer-checked:bg-blue-600 peer-focus:bg-blue-600 -> Option D

4. Quick Check:

   Use peer-checked and peer-focus for sibling states [OK]

Hint: Combine peer-checked and peer-focus for sibling states [OK]

Common Mistakes:

• Using focus:bg-blue-600 instead of peer-focus
• Using checked:bg-blue-600 without peer prefix
• Confusing focus-within with peer-focus