If statement in Javascript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the number is positive.

Javascript

if (number [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 '<' will check for negative numbers instead.

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

The '>' operator checks if the number is greater than zero, meaning it is positive.

2fill in blank

medium

Complete the code to print 'Even' if the number is divisible by 2.

Javascript

if (number [1] 2 === 0) {
  console.log('Even');
}

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

A%

B+

C-

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+' or '-' will not check divisibility.

Using '*' multiplies numbers, not checks remainder.

The '%' operator gives the remainder. If remainder is 0 when divided by 2, number is even.

3fill in blank

hard

Fix the error in the if statement to check if age is at least 18.

Javascript

if (age [1] 18) {
  console.log('Adult');
}

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

A<

B<=

C>=

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' or '<=' checks for younger than 18.

Using '==' checks only exactly 18, not older.

The '>=' operator checks if age is greater than or equal to 18, meaning adult or older.

4fill in blank

hard

Fill both blanks to print 'Teenager' if age is between 13 and 19 inclusive.

Javascript

if (age [1] 13 && age [2] 19) {
  console.log('Teenager');
}

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

A>=

B<

C<=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' for the first blank would exclude 13.

Using '>' for the second blank would exclude 19.

Use '>=' to check age is at least 13 and '<=' to check age is at most 19.

5fill in blank

hard

Fill the blanks to print 'Grade A' if score is above 90, 'Grade B' if score is above 80, else 'Grade C'.

Javascript

if (score [1] 90) {
  console.log('Grade A');
} else if (score [2] 80) {
  console.log('Grade B');
} else {
  console.log('Grade C');
}

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

A>

B>=

C<=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>=' would include boundary scores incorrectly.

Using '<=' in the blanks would cause wrong grade assignments.

Use '>' to check if score is strictly greater than 90 for A and greater than 80 for B.

Practice

1. What does an if statement do in JavaScript?

easy

A. Declares a variable

B. Repeats code multiple times

C. Defines a new function

D. Runs code only if a condition is true

Solution

1. Step 1: Understand the purpose of an if statement

   An if statement checks a condition and runs code only when that condition is true.

2. Step 2: Compare options with the definition

   Only Runs code only if a condition is true matches this behavior exactly.

3. Final Answer:

   Runs code only if a condition is true -> Option D

4. Quick Check:

   If statement = runs code if true [OK]

Hint: If it runs code only when true, it's an if statement [OK]

Common Mistakes:

• Confusing if with loops
• Thinking if declares variables
• Mixing if with function definitions

2. Which of the following is the correct syntax for an if statement in JavaScript?

easy

A. if condition { console.log('Yes'); }

B. if (condition) console.log('Yes');

C. if condition: console.log('Yes');

D. if (condition) then { console.log('Yes'); }

Solution

1. Step 1: Recall JavaScript if syntax

   The condition must be inside parentheses, and the code block can be inside curly braces or a single statement without braces.

2. Step 2: Check each option

   if (condition) console.log('Yes'); correctly uses parentheses around the condition and a statement without braces.

3. Final Answer:

   if (condition) console.log('Yes'); -> Option B

4. Quick Check:

   Parentheses around condition = correct syntax [OK]

Hint: Condition must be in parentheses for if [OK]

Common Mistakes:

• Omitting parentheses around condition
• Using colons instead of braces
• Adding 'then' keyword (not in JS)

3. What will be the output of this code?

let x = 10;
if (x > 5) {
  console.log('Big');
} else {
  console.log('Small');
}

medium

A. Small

B. 10

C. Big

D. No output

Solution

1. Step 1: Evaluate the condition x > 5

   Since x is 10, which is greater than 5, the condition is true.

2. Step 2: Determine which block runs

   The if block runs and prints 'Big'. The else block is skipped.

3. Final Answer:

   Big -> Option C

4. Quick Check:

   10 > 5 is true, so output is 'Big' [OK]

Hint: Check if condition is true to pick output [OK]

Common Mistakes:

• Choosing else output when condition is true
• Confusing variable value with output
• Ignoring else block

4. Find the error in this code:

if x == 5 {
  console.log('Equal');
}

medium

A. Missing parentheses around condition

B. Using double equals instead of triple equals

C. Missing semicolon after console.log

D. Curly braces should be parentheses

Solution

1. Step 1: Check if statement syntax

   In JavaScript, the condition must be inside parentheses after if.

2. Step 2: Identify the error

   The code misses parentheses around x == 5, causing a syntax error.

3. Final Answer:

   Missing parentheses around condition -> Option A

4. Quick Check:

   Condition needs parentheses in if [OK]

Hint: Always put condition inside parentheses in if [OK]

Common Mistakes:

• Omitting parentheses around condition
• Confusing == and === (both valid but different)
• Thinking semicolon is mandatory after console.log

5. You want to print 'Adult' if age is 18 or more, otherwise 'Minor'. Which code correctly uses an if statement?

hard

A. if (age >= 18) { console.log('Adult'); } else { console.log('Minor'); }

B. if age >= 18 then { console.log('Adult'); } else { console.log('Minor'); }

C. if (age > 18) { console.log('Adult'); } else { console.log('Minor'); }

D. if (age = 18) { console.log('Adult'); } else { console.log('Minor'); }

Solution

1. Step 1: Check condition for age 18 or more

   The condition should be age >= 18 to include 18 and above.

2. Step 2: Verify syntax and logic

   if (age >= 18) { console.log('Adult'); } else { console.log('Minor'); } uses correct syntax and condition. if age >= 18 then { console.log('Adult'); } else { console.log('Minor'); } uses invalid 'then'. if (age > 18) { console.log('Adult'); } else { console.log('Minor'); } excludes age 18. if (age = 18) { console.log('Adult'); } else { console.log('Minor'); } uses assignment (=) instead of comparison (== or >=).

3. Final Answer:

   if (age >= 18) { console.log('Adult'); } else { console.log('Minor'); } -> Option A

4. Quick Check:

   Use >= and correct syntax for if-else [OK]

Hint: Use >= for 18 or more, no 'then' keyword [OK]

Common Mistakes:

• Using assignment (=) instead of comparison
• Using 'then' keyword (not in JS)
• Using > instead of >= to include 18