Comparison operators in Javascript - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of chained comparison with mixed types

What is the output of this JavaScript code?

console.log(3 < 4 < 5);

Javascript

console.log(3 < 4 < 5);

A TypeError

B undefined

C false

D true

💡 Hint

Remember that JavaScript evaluates comparisons from left to right and converts booleans to numbers in some cases.

The expression 3 < 4 is true, which converts to 1 when compared to 5. Then 1 < 5 is true, so the final output is true. But the code is console.log(3 < 4 < 5), which evaluates as (3 < 4) < 5 → true < 5 → 1 < 5 → true. So the output is true, but the question asks for the output of the code exactly. The code outputs true, so option D is correct.

❓ Predict Output

intermediate

Output of strict equality with different types

What is the output of this JavaScript code?

console.log('5' === 5);

Javascript

console.log('5' === 5);

A true

B false

C TypeError

D undefined

💡 Hint

Strict equality checks both value and type.

The string '5' and the number 5 have different types, so strict equality === returns false.

❓ Predict Output

advanced

Output of comparing objects with == and ===

What is the output of this JavaScript code?

const a = {};
const b = {};
console.log(a == b);
console.log(a === b);

Javascript

const a = {};
const b = {};
console.log(a == b);
console.log(a === b);

A false\ntrue

B true\ntrue

C false\nfalse

D true\nfalse

💡 Hint

Objects are compared by reference, not by content.

Both == and === compare object references. Since a and b are different objects, both comparisons return false.

❓ Predict Output

advanced

Output of comparing null and undefined with == and ===

What is the output of this JavaScript code?

console.log(null == undefined);
console.log(null === undefined);

Javascript

console.log(null == undefined);
console.log(null === undefined);

A true\nfalse

B false\nfalse

C true\ntrue

D false\ntrue

💡 Hint

== allows type coercion, === does not.

null == undefined is true because == treats them as equal. null === undefined is false because they have different types.

❓ Predict Output

expert

Output of comparing NaN with itself

What is the output of this JavaScript code?

console.log(NaN == NaN);
console.log(NaN === NaN);
console.log(Object.is(NaN, NaN));

Javascript

console.log(NaN == NaN);
console.log(NaN === NaN);
console.log(Object.is(NaN, NaN));

A false\nfalse\ntrue

B true\ntrue\ntrue

C true\nfalse\nfalse

D false\ntrue\nfalse

💡 Hint

NaN is not equal to anything, even itself, except with Object.is.

NaN == NaN and NaN === NaN both return false. Object.is(NaN, NaN) returns true.