Nested conditional statements in Javascript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if a number is positive.

Javascript

if (num [1] 0) {
  console.log('Positive number');
}

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

A<

B>

C===

D!==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' will check for negative numbers.

Using '===' checks for equality, not greater than.

The condition num > 0 checks if the number is positive.

2fill in blank

medium

Complete the code to check if a number is positive and even.

Javascript

if (num > 0) {
  if (num [1] 2 === 0) {
    console.log('Positive even number');
  }
}

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

A%

B/

C*

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using division / instead of modulus %.

Using multiplication or subtraction operators incorrectly.

The modulus operator % checks the remainder. If num % 2 === 0, the number is even.

3fill in blank

hard

Fix the error in the nested condition to check if a number is negative and odd.

Javascript

if (num [1] 0) {
  if (num % 2 !== 0) {
    console.log('Negative odd number');
  }
}

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

A<

B!==

C>

D===

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' instead of '<' to check for negative numbers.

Using equality operators instead of comparison.

The condition num < 0 checks if the number is negative.

4fill in blank

hard

Fill both blanks to check if a number is zero or positive and even.

Javascript

if (num [1] 0) {
  if (num [2] 2 === 0) {
    console.log('Zero or positive even number');
  }
}

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

A>=

B<

C%

D===

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>=' for the first condition.

Using division instead of modulus for even check.

The first condition num >= 0 checks for zero or positive numbers. The second condition uses % to check if the number is even.

5fill in blank

hard

Fill all three blanks to check if a number is positive, even, and less than 100.

Javascript

if (num [1] 0) {
  if (num [2] 2 === 0 && num [3] 100) {
    console.log('Positive even number less than 100');
  }
}

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

A>

B%

C<

D===

Attempts:

3 left

💡 Hint

Common Mistakes

Using division instead of modulus for even check.

Using '>=' instead of '>' for positivity.

Using '>' instead of '<' for less than 100.

The first condition checks if num > 0 (positive). The second uses % to check evenness. The third checks if num < 100.

Practice

1. What does a nested conditional statement mean in JavaScript?
if (condition1) { if (condition2) { /* code */ } }

easy

A. A loop inside a condition

B. A condition inside another condition

C. Two conditions checked at the same time

D. A function inside a condition

Solution

1. Step 1: Understand the structure of nested conditionals

   Nested conditionals mean one if statement is placed inside another if statement's block.

2. Step 2: Identify the meaning of the code snippet

   The code checks condition1 first, and only if true, it checks condition2 inside it.

3. Final Answer:

   A condition inside another condition -> Option B

4. Quick Check:

   Nested conditional = condition inside condition [OK]

Hint: Look for if inside another if block [OK]

Common Mistakes:

• Thinking nested means conditions checked together
• Confusing nested conditionals with loops
• Assuming functions are involved

2. Which of the following is the correct syntax for nested if statements in JavaScript?

easy

A. if (a > 0) { if (b > 0) { console.log('Both positive'); } }

B. if (a > 0) if (b > 0) console.log('Both positive'); }

C. if (a > 0) { if (b > 0) console.log('Both positive'); } else }

D. if a > 0 { if b > 0 { console.log('Both positive'); } }

Solution

1. Step 1: Check proper use of braces and parentheses

   if (a > 0) { if (b > 0) { console.log('Both positive'); } } uses parentheses for conditions and braces to group code blocks correctly.

2. Step 2: Verify syntax correctness

   The other options have missing or misplaced braces or parentheses causing syntax errors.

3. Final Answer:

   if (a > 0) { if (b > 0) { console.log('Both positive'); } } -> Option A

4. Quick Check:

   Correct nested if syntax = if (a > 0) { if (b > 0) { console.log('Both positive'); } } [OK]

Hint: Match each if with parentheses and braces [OK]

Common Mistakes:

• Missing braces for inner if block
• Omitting parentheses around conditions
• Extra or misplaced braces

3. What will be the output of this code?

let x = 5;
if (x > 0) {
  if (x < 10) {
    console.log('A');
  } else {
    console.log('B');
  }
} else {
  console.log('C');
}

medium

A. No output

B. B

C. C

D. A

Solution

1. Step 1: Evaluate the outer if condition

   x = 5, which is greater than 0, so the outer if block runs.

2. Step 2: Evaluate the inner if condition

   Inside, x < 10 is true (5 < 10), so it prints 'A'.

3. Final Answer:

   A -> Option D

4. Quick Check:

   5 > 0 and 5 < 10 prints 'A' [OK]

Hint: Check outer condition first, then inner [OK]

Common Mistakes:

• Ignoring inner else block
• Confusing output with 'B' or 'C'
• Assuming no output if conditions are true

4. Find the error in this nested conditional code:

let num = 10;
if (num > 5) {
  if num < 15 {
    console.log('Inside range');
  }
}

medium

A. Using console.log incorrectly

B. Missing braces for outer if block

C. Missing parentheses around inner if condition

D. No error, code is correct

Solution

1. Step 1: Check syntax of inner if statement

   Inner if is written as if num < 15 { missing parentheses around condition.

2. Step 2: Confirm correct syntax for if statements

   JavaScript requires parentheses around conditions: if (num < 15) {.

3. Final Answer:

   Missing parentheses around inner if condition -> Option C

4. Quick Check:

   if conditions need parentheses [OK]

Hint: Always put parentheses around if conditions [OK]

Common Mistakes:

• Forgetting parentheses in if conditions
• Assuming braces are optional
• Thinking console.log causes error

5. You want to write a nested conditional that prints:
- 'Small positive' if a number is > 0 and < 10
- 'Large positive' if a number is >= 10
- 'Non-positive' otherwise
Which code correctly implements this?

hard

A. if (num > 0) { if (num < 10) { console.log('Small positive'); } else { console.log('Large positive'); } } else { console.log('Non-positive'); }

B. if (num > 0 && num < 10) { console.log('Small positive'); } else if (num >= 10) { console.log('Large positive'); } else { console.log('Non-positive'); }

C. if (num > 0) { if (num <= 10) { console.log('Small positive'); } else { console.log('Large positive'); } } else { console.log('Non-positive'); }

D. if (num >= 0) { if (num < 10) { console.log('Small positive'); } else { console.log('Large positive'); } } else { console.log('Non-positive'); }

Solution

1. Step 1: Check conditions for small positive numbers

   if (num > 0) { if (num < 10) { console.log('Small positive'); } else { console.log('Large positive'); } } else { console.log('Non-positive'); } checks if num > 0, then inside if num < 10 to print 'Small positive'.

2. Step 2: Check conditions for large positive and non-positive

   Else inside outer if prints 'Large positive' for num >= 10, else prints 'Non-positive'.

3. Step 3: Verify other options

   The option with combined conditions (&& and else if) is logically correct but does not use nested if statements. The option with outer condition num >= 0 incorrectly classifies 0 as 'Small positive'. The option with inner condition num <= 10 incorrectly classifies 10 as 'Small positive'.

4. Final Answer:

   if (num > 0) { if (num < 10) { console.log('Small positive'); } else { console.log('Large positive'); } } else { console.log('Non-positive'); } -> Option A

5. Quick Check:

   Nested if with correct ranges = if (num > 0) { if (num < 10) { console.log('Small positive'); } else { console.log('Large positive'); } } else { console.log('Non-positive'); } [OK]

Hint: Check each condition range carefully in nested ifs [OK]

Common Mistakes:

• Using <= instead of < for small positive
• Including zero as positive
• Not nesting conditions properly