JavaScript JavaScript 5

Question 1

What is the output of `console.log(typeof function(){})` in JavaScript?

Accepted Answer

'function'

Answer

`typeof` returns `'function'` for function objects, making them distinguishable from plain objects.

Question 2

What does the `this` keyword refer to inside an arrow function?

Accepted Answer

The `this` value of the enclosing lexical scope

Answer

Arrow functions do not have their own `this` binding — they inherit `this` from the surrounding lexical context where they are defined.

Question 3

Which of the following correctly creates a new Promise that resolves after 1 second?

Accepted Answer

new Promise(resolve => setTimeout(resolve, 1000))

Answer

You wrap `setTimeout` inside a `new Promise` constructor and call `resolve` inside the timeout callback.

Question 4

What is prototype-based inheritance in JavaScript?

Accepted Answer

A system where objects inherit directly from other objects via a prototype chain

Answer

JavaScript uses prototype-based inheritance where each object has an internal `[[Prototype]]` link to another object from which it inherits properties.

Question 5

What does `localStorage.setItem('key', value)` require about the value?

Accepted Answer

It must be a string — non-string values are automatically converted

Answer

`localStorage` can only store strings; passing a non-string value causes it to be coerced via `.toString()`, which is why objects should be stringified manually.

JavaScript Practice Test

JavaScript Practice Test

JavaScript JavaScript 5