Logical AND rendering in React - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to render the message only if show is true.

React

return (
  <div>
    {show [1] <p>Hello!</p>}
  </div>
);

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

A|

B||

C?

D&&

Attempts:

3 left

💡 Hint

Common Mistakes

Using || will render the right side even if the condition is false.

Using ? is for ternary expressions, not simple AND rendering.

The logical AND operator (&&) renders the right side only if the left side is true.

2fill in blank

medium

Complete the code to render Loading... only when isLoading is true.

React

return (
  <div>
    {isLoading [1] <span>Loading...</span>}
  </div>
);

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

A||

B!

C&&

D?

Attempts:

3 left

💡 Hint

Common Mistakes

Using || will show the content even if isLoading is false.

Using ! negates the condition, which is not what we want here.

Using && ensures Loading... shows only when isLoading is true.

3fill in blank

hard

Fix the error in the code to render Welcome back! only if isLoggedIn is true.

React

return (
  <div>
    {isLoggedIn [1] <p>Welcome back!</p>}
  </div>
);

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

A&&

B||

C?

D|

Attempts:

3 left

💡 Hint

Common Mistakes

Using || causes the message to always render.

Using | is a bitwise operator and causes errors.

Logical AND (&&) correctly renders the message only when isLoggedIn is true.

4fill in blank

hard

Fill both blanks to render Admin Panel only if isAdmin is true and isLoggedIn is true.

React

return (
  <div>
    {isAdmin [1] isLoggedIn [2] <h1>Admin Panel</h1>}
  </div>
);

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

A&&

B||

C?

D!

Attempts:

3 left

💡 Hint

Common Mistakes

Using || would show the panel if either condition is true.

Using ? is for ternary expressions, not chaining conditions.

Using && between both conditions ensures the panel shows only if both are true.

5fill in blank

hard

Fill all three blanks to render Special Offer only if isMember is true, hasCoupon is true, and isLoggedIn is true.

React

return (
  <div>
    {isMember [1] hasCoupon [2] isLoggedIn [3] <div>Special Offer</div>}
  </div>
);

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

A||

B&&

Attempts:

3 left

💡 Hint

Common Mistakes

Using || would show the offer if any condition is true.

Mixing operators causes unexpected rendering.

All three conditions must be true, so use && between each condition.

Practice

1. What does the logical AND operator && do in React JSX rendering?

easy

A. It renders the left side only if the right side is false.

B. It always renders both sides regardless of the condition.

C. It renders the right side only if the left side condition is true.

D. It throws an error if the left side is false.

Solution

1. Step 1: Understand logical AND in JSX

   In React, condition && expression means the expression renders only if the condition is true.

2. Step 2: Apply to rendering behavior

   If the condition is false, React skips rendering the expression, keeping UI clean.

3. Final Answer:

   It renders the right side only if the left side condition is true. -> Option C

4. Quick Check:

   Logical AND rendering = conditional display [OK]

Hint: Remember: left true shows right, left false shows nothing [OK]

Common Mistakes:

• Thinking both sides always render
• Confusing left and right side roles
• Expecting error on false condition

2. Which of the following is the correct syntax to conditionally render <Message /> only if show is true using logical AND in React?

easy

A. {show ? <Message /> : null}

B. {show && <Message />}

C. {show || <Message />}

D. {show && Message()}

Solution

1. Step 1: Identify logical AND syntax

   The correct syntax uses {condition && <Component />} to render conditionally.

2. Step 2: Check each option

   {show && <Message />} uses {show && <Message />}, which is correct. {show ? <Message /> : null} uses ternary, valid but not logical AND. {show || <Message />} uses OR, wrong logic. {show && Message()} calls function, not JSX element.

3. Final Answer:

   {show && <Message />} -> Option B

4. Quick Check:

   Logical AND syntax = {condition && JSX} [OK]

Hint: Look for {condition && } pattern [OK]

Common Mistakes:

• Using OR (||) instead of AND (&&)
• Calling component as function without JSX
• Confusing ternary with logical AND

3. Given the code snippet:
<pre>const isLoggedIn = false;
return (
<div>
{isLoggedIn && <p>Welcome back!</p>}
</div>
);
What will be rendered in the browser?

medium

A.

B. Syntax error

C. Welcome back!

D. Welcome back!

Solution

1. Step 1: Evaluate the condition value

   The variable isLoggedIn is false, so the left side of && is false.

2. Step 2: Understand logical AND rendering

   Since the condition is false, React renders nothing for that expression, so only the <div> with no children appears.

3. Final Answer:

   <div></div> -> Option A

4. Quick Check:

   False && JSX = no render [OK]

Hint: False condition means no JSX rendered [OK]

Common Mistakes:

• Expecting the paragraph to render anyway
• Confusing false with null rendering
• Thinking it causes an error

4. Identify the error in this React code snippet:

const show = true;
return (
  <div>
    {show &<p>Hello</p>}
  </div>
);

medium

A. No error, code works fine

B. Missing space between & and <p> causes syntax error

C. The <p> tag cannot be used inside JSX

D. Using single & instead of && is invalid in JSX

Solution

1. Step 1: Check operator usage

   The code uses a single ampersand & instead of double && for logical AND, which is invalid in JSX.

2. Step 2: Understand JSX syntax rules

   JSX requires && for logical AND; single & is a bitwise operator and causes syntax error here.

3. Final Answer:

   Using single & instead of && is invalid in JSX -> Option D

4. Quick Check:

   Logical AND needs &&, not & [OK]

Hint: Use && for logical AND in JSX, not & [OK]

Common Mistakes:

• Using single & instead of &&
• Thinking <p> tags are invalid in JSX
• Ignoring syntax errors from operators

5. You want to render a <Warning /> component only if showWarning is true and userRole is 'admin'. Which of these is the correct logical AND rendering expression in React?

hard

A. {showWarning && userRole === 'admin' && <Warning />}

B. {showWarning || userRole === 'admin' && <Warning />}

C. {(showWarning && userRole) === 'admin' && <Warning />}

D. {showWarning && (userRole = 'admin') && <Warning />}

Solution

1. Step 1: Understand multiple conditions with logical AND

   To render only if both conditions are true, chain them with &&: showWarning && userRole === 'admin'.

2. Step 2: Evaluate each option

   {showWarning && userRole === 'admin' && <Warning />} correctly chains both conditions and renders <Warning />. {showWarning || userRole === 'admin' && <Warning />} uses OR, which is wrong logic. {(showWarning && userRole) === 'admin' && <Warning />} compares the whole expression incorrectly. {showWarning && (userRole = 'admin') && <Warning />} uses assignment = instead of comparison ===.

3. Final Answer:

   {showWarning && userRole === 'admin' && <Warning />} -> Option A

4. Quick Check:

   Chain conditions with && for multiple checks [OK]

Hint: Chain conditions with &&, use === for comparison [OK]

Common Mistakes:

• Using || instead of && for all conditions
• Using assignment = instead of comparison ===
• Incorrect grouping of conditions