Logical operators in Javascript - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of combined logical operators

What is the output of the following JavaScript code?

Javascript

const a = true;
const b = false;
const c = true;
console.log(a && b || c);

A true

B false

C undefined

D TypeError

💡 Hint

Remember that && has higher precedence than || in JavaScript.

The expression evaluates as (a && b) || c. Since a && b is false, the result is false || true, which is true.

❓ Predict Output

intermediate

Logical NOT and OR combination

What will be logged to the console?

Javascript

const x = false;
const y = true;
console.log(!x || y);

A true

B false

C undefined

D SyntaxError

💡 Hint

The ! operator flips the boolean value.

!x is true because x is false, so true || true is true.

❓ Predict Output

advanced

Short-circuit evaluation with logical AND

What is the output of this code snippet?

Javascript

function test() {
  console.log('Function called');
  return true;
}

const result = false && test();
console.log(result);

A true

B false

C Function called\nfalse

D ReferenceError

💡 Hint

Logical AND stops evaluating if the first operand is false.

Since the first operand is false, test() is not called, so only false is logged.

❓ Predict Output

advanced

Logical OR with falsy values

What will be the output of this code?

Javascript

const val = 0 || '' || null || undefined || 'default';
console.log(val);

A 0

B null

C default

D undefined

💡 Hint

Logical OR returns the first truthy value.

All values before 'default' are falsy, so 'default' is returned.

🧠 Conceptual

expert

Understanding logical operator precedence and output

Consider the code below. What is the value of variable result after execution?

Javascript

const result = false || true && false || true;

A TypeError

B false

C undefined

D true

💡 Hint

Remember that && has higher precedence than ||, so evaluate that part first.

true && false is false, so expression becomes false || false || true, which evaluates to true.