If statement in Javascript - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested if statements

What is the output of the following code?

Javascript

let x = 10;
if (x > 5) {
  if (x < 15) {
    console.log('A');
  } else {
    console.log('B');
  }
} else {
  console.log('C');
}

A B

B A

C C

D No output

💡 Hint

Check the conditions step by step.

x is 10, which is greater than 5 and less than 15, so the first if and nested if both run, printing 'A'.

❓ Predict Output

intermediate

If statement with else if

What will be logged to the console?

Javascript

let score = 75;
if (score >= 90) {
  console.log('Excellent');
} else if (score >= 70) {
  console.log('Good');
} else {
  console.log('Try again');
}

A Good

B Excellent

C Try again

D No output

💡 Hint

Check which condition matches the score first.

Score is 75, which is not >= 90 but is >= 70, so 'Good' is printed.

❓ Predict Output

advanced

If statement with logical operators

What is the output of this code?

Javascript

let a = 5;
let b = 10;
if (a > 3 && b < 15) {
  console.log('X');
} else if (a > 3 || b > 15) {
  console.log('Y');
} else {
  console.log('Z');
}

A No output

B Z

C X

D Y

💡 Hint

Both conditions in the first if must be true for 'X'.

a is 5 > 3 and b is 10 < 15, so first if condition is true, printing 'X'.

❓ Predict Output

advanced

If statement with type coercion

What will be the output of this code?

Javascript

let val = '0';
if (val) {
  console.log('True');
} else {
  console.log('False');
}

A True

B False

C SyntaxError

D No output

💡 Hint

Check how JavaScript treats non-empty strings in conditions.

Non-empty strings are truthy in JavaScript, so 'True' is printed.

❓ Predict Output

expert

If statement with variable scope

What is the value of x after running this code?

Javascript

let x = 1;
if (true) {
  let x = 2;
  if (true) {
    x = 3;
  }
}
console.log(x);

A 2

B ReferenceError

C 3

D 1

💡 Hint

Consider the scope of variables declared with let inside blocks.

The inner x variables are block scoped and do not affect the outer x, so x remains 1.

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