JavaScript JavaScript 2

Question 1

What does the `typeof null` expression return in JavaScript?

Accepted Answer

'object'

Answer

`typeof null` returns 'object' due to a long-standing bug in JavaScript's original implementation.

Question 2

Which array method creates a new array by calling a function on every element of the original array?

Accepted Answer

map()

Answer

`Array.prototype.map()` returns a new array with each element transformed by the provided callback.

Question 3

What is the output of `console.log(0.1 + 0.2 === 0.3)` in JavaScript?

Accepted Answer

false

Answer

Due to floating-point precision limitations, `0.1 + 0.2` equals `0.30000000000000004`, not exactly `0.3`.

Question 4

What does the `Array.prototype.reduce()` method do?

Accepted Answer

Executes a reducer function on each element, accumulating a single result

Answer

`reduce()` applies a callback with an accumulator to each element, ultimately returning a single accumulated value.

Question 5

Which keyword is used to define a named function expression in JavaScript?

Accepted Answer

function

Answer

JavaScript uses the `function` keyword to define both function declarations and function expressions.

JavaScript Practice Test