JavaScript JavaScript 4

Question 1

What is the difference between `==` and `===` in JavaScript?

Accepted Answer

`==` checks value only; `===` checks value AND type

Answer

`==` performs type coercion before comparing, while `===` (strict equality) requires both value and type to match.

Question 2

What will `console.log([] + [])` output in JavaScript?

Accepted Answer

''

Answer

Both arrays are coerced to empty strings, and concatenating two empty strings yields an empty string `''`.

Question 3

Which built-in method removes and returns the LAST element of an array?

Accepted Answer

pop()

Answer

`Array.prototype.pop()` removes the last element from an array and returns that element, mutating the original array.

Question 4

What is event delegation in JavaScript?

Accepted Answer

Attaching a single event listener to a parent element to handle events from its children

Answer

Event delegation attaches one listener to a parent element and uses the event's `target` property to identify which child triggered it, improving performance.

Question 5

What does `Array.isArray([])` return?

Accepted Answer

true

Answer

`Array.isArray()` reliably returns `true` for arrays, unlike `typeof` which returns `'object'` for arrays.

JavaScript Practice Test

JavaScript Practice Test

JavaScript JavaScript 4