If conditions in JSX in React - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

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

React

function Greeting({ showMessage }) {
  return (
    <div>
      {showMessage && [1]
    </div>
  );
}

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

A<p>Hello, world!</p>

B<p>Hello, friend!</p>

C<p>Welcome back!</p>

D<p>Goodbye!</p>

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to wrap the message in JSX tags.

Using a string without JSX tags.

The expression uses logical AND to render the

Hello, world!

only if showMessage is true.

2fill in blank

medium

Complete the code to render Loading... if isLoading is true, otherwise render Data loaded.

React

function Loader({ isLoading }) {
  return (
    <div>
      {isLoading ? [1] : <p>Data loaded</p>}
    </div>
  );
}

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

ALoading...

B"Loading..."

C<span>Loading</span>

D<p>Loading...</p>

Attempts:

3 left

💡 Hint

Common Mistakes

Using plain strings without JSX tags.

Forgetting the colon ':' in the ternary operator.

The ternary operator renders the JSX

Loading...

when isLoading is true.

3fill in blank

hard

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

React

function Welcome({ isLoggedIn }) {
  return (
    <div>
      {isLoggedIn && [1]
    </div>
  );
}

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

A<p>Welcome back!</p>

B"Welcome back!"

CWelcome back!

D<Welcome back! />

Attempts:

3 left

💡 Hint

Common Mistakes

Using plain strings without JSX tags.

Trying to use invalid JSX syntax like .

JSX requires elements to be wrapped in tags. Using

Welcome back!

is correct.

4fill in blank

hard

Fill both blanks to render Admin Panel if isAdmin is true, otherwise render User Panel.

React

function Panel({ isAdmin }) {
  return (
    <div>
      {isAdmin ? [1] : [2]
    </div>
  );
}

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

A<h1>Admin Panel</h1>

B<h2>User Panel</h2>

C<h1>User Panel</h1>

D<h2>Admin Panel</h2>

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the tags or texts for admin and user panels.

Using strings instead of JSX elements.

The ternary operator chooses between

Admin Panel

and

User Panel

based on isAdmin.

5fill in blank

hard

Fill all three blanks to render a greeting with the user's name if isLoggedIn is true, otherwise show a login button.

React

function UserGreeting({ isLoggedIn, userName }) {
  return (
    <div>
      {isLoggedIn ? <p>Hello, [1]!</p> : <button [2]>[3]</button>}
    </div>
  );
}

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

AuserName

Baria-label="login button"

CLog in

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string 'userName' instead of the variable userName.

Forgetting the aria-label attribute on the button.

Using incorrect button text.

The greeting uses the userName variable, the button has an aria-label for accessibility, and the button text is 'Log in'.

Practice

1. Which of the following is the correct way to conditionally render a message in JSX when isLoggedIn is true?

easy

A. {if (isLoggedIn) <p>Welcome back!</p>}

B. {isLoggedIn && <p>Welcome back!</p>}

C. {isLoggedIn ? <p>Welcome back!</p>}

D. {isLoggedIn || <p>Welcome back!</p>}

Solution

1. Step 1: Understand JSX conditional rendering with &&

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

2. Step 2: Check each option's syntax

   {isLoggedIn && <p>Welcome back!</p>} uses {isLoggedIn && <p>Welcome back!</p>}, which is correct. {if (isLoggedIn) <p>Welcome back!</p>} uses an invalid if statement inside JSX. {isLoggedIn ? <p>Welcome back!</p>} uses an incomplete ternary operator without the false branch (`: expression`), causing a syntax error. {isLoggedIn || <p>Welcome back!</p>} uses ||, which is incorrect for this purpose.

3. Final Answer:

   {isLoggedIn && <p>Welcome back!</p>} -> Option B

4. Quick Check:

   Use && for simple true condition rendering [OK]

Hint: Use && to show content only if true [OK]

Common Mistakes:

• Trying to use if statements directly inside JSX
• Using || instead of && for conditional rendering
• Confusing ternary with && when only one condition is needed

2. Which JSX snippet correctly uses a ternary operator to show <p>Hello</p> if showHello is true, otherwise <p>Goodbye</p>?

easy

A. {showHello && <p>Hello</p> else <p>Goodbye</p>}

B. {showHello ? <p>Goodbye</p> : <p>Hello</p>}

C. {if (showHello) <p>Hello</p> else <p>Goodbye</p>}

D. {showHello ? <p>Hello</p> : <p>Goodbye</p>}

Solution

1. Step 1: Understand ternary syntax in JSX

   The ternary operator syntax is condition ? expressionIfTrue : expressionIfFalse.

2. Step 2: Match the expressions to the condition

   {showHello ? <p>Hello</p> : <p>Goodbye</p>} correctly shows Hello if showHello is true, else Goodbye. {showHello && <p>Hello</p> else <p>Goodbye</p>} uses invalid syntax with else inside JSX. {if (showHello) <p>Hello</p> else <p>Goodbye</p>} tries to use if statement inside JSX, which is invalid. {showHello ? <p>Goodbye</p> : <p>Hello</p>} reverses the messages.

3. Final Answer:

   {showHello ? <p>Hello</p> : <p>Goodbye</p>} -> Option D

4. Quick Check:

   Ternary = condition ? true : false [OK]

Hint: Ternary: condition ? true : false for two choices [OK]

Common Mistakes:

• Using if/else statements directly inside JSX
• Swapping true and false expressions
• Using && when two choices are needed

3. What will be rendered by this React component?

function Greeting({ isMorning }) {
  return (
    <div>
      {isMorning ? <h1>Good morning!</h1> : <h1>Good evening!</h1>}
      {isMorning && <p>Have a nice day!</p>}
    </div>
  );
}

If isMorning is false?

medium

A. Good evening!

B. Good evening!Have a nice day!

C. Good morning!Have a nice day!

D. Good morning!

Solution

1. Step 1: Evaluate the ternary expression with isMorning = false

   The ternary isMorning ? <h1>Good morning!</h1> : <h1>Good evening!</h1> renders <h1>Good evening!</h1> because isMorning is false.

2. Step 2: Evaluate the && expression with isMorning = false

   The expression isMorning && <p>Have a nice day!</p> renders nothing because isMorning is false.

3. Final Answer:

   <div><h1>Good evening!</h1></div> -> Option A

4. Quick Check:

   False && anything = nothing [OK]

Hint: False && expression renders nothing; ternary picks false branch [OK]

Common Mistakes:

• Assuming && renders content when condition is false
• Mixing up ternary true/false branches
• Expecting both expressions to render always

4. Identify the error in this JSX snippet:

return (
  <div>
    {isActive ? <p>Active</p>}
  </div>
);

medium

A. No error, code is valid

B. Using if statement inside JSX

C. Missing else part in ternary operator

D. Incorrect use of && operator

Solution

1. Step 1: Check ternary operator syntax

   The ternary operator requires both true and false expressions: condition ? exprIfTrue : exprIfFalse. Here, the false part is missing.

2. Step 2: Understand JSX requirements

   Without the false expression, JSX will throw a syntax error because the ternary is incomplete.

3. Final Answer:

   Missing else part in ternary operator -> Option C

4. Quick Check:

   Ternary needs both ? and : parts [OK]

Hint: Ternary must have both ? and : parts [OK]

Common Mistakes:

• Omitting the else (false) part in ternary
• Confusing ternary with && operator
• Trying to use if statements inside JSX

5. You want to render a list of user names, but only show the name if the user is active. Which JSX code correctly implements this using map and conditional rendering?

hard

A. {users.map(user => user.isActive ? <li key={user.id}>{user.name}</li> : null)}

B. {users.map(user => if (user.isActive) return <li key={user.id}>{user.name}</li> )}

C. {users.map(user => user.isActive || <li>{user.name}</li>)}

D. {users.map(user => user.isActive ? <li>{user.name}</li> : <li>Inactive</li>)}

Solution

1. Step 1: Understand conditional rendering inside map

   To render only active users, use a ternary that returns the list item or null.

2. Step 2: Check key usage and syntax

   {users.map(user => user.isActive ? <li key={user.id}>{user.name}</li> : null)} correctly uses key={user.id} and returns null for inactive users, which React ignores.

3. Step 3: Analyze other options

   {users.map(user => if (user.isActive) return <li key={user.id}>{user.name}</li> )} uses invalid syntax: `if` statement directly after arrow function requires block `{}` braces. {users.map(user => user.isActive || <li>{user.name}</li>)} uses `||` which renders items for inactive users and misses keys. {users.map(user => user.isActive ? <li>{user.name}</li> : <li>Inactive</li>)} shows inactive users with text, which is not desired.

4. Final Answer:

   {users.map(user => user.isActive ? <li key={user.id}>{user.name}</li> : null)} -> Option A

5. Quick Check:

   Use ternary with key and null for conditional list rendering [OK]

Hint: Use ternary with key and null to skip items [OK]

Common Mistakes:

• Missing key prop in list items
• Using if statements inside map without return
• Rendering false or undefined instead of null