Node

Question 1

What is an Event loop in Node.js and how does it work?

Answer 1

An event loop in Node.js handles all the asynchronous callbacks in an application

Question 2

Explain the purpose of module.exports?

Answer 2

A module in Node.js is used to encapsulate all the related codes into a single unit of code

Question 3

Explain libuv

Answer 3

Libuv is a multi-platform support library of Node.js which majorly is used for asynchronous I/O

Question 4

What are 5 features of libuv?

Answer 4

Full-featured event loop backed
File system events
Asynchronous file & file system operations
Asynchronous TCP & UDP sockets
Child processes

Question 5

Explain the difference between “==” and “===”?

Answer 5

”==” checks only for equality in value whereas “===” is a stricter equality test and returns false if either the value or the type of the two variables are different.

Question 6

How will you explain closures in JavaScript? When are they used?

Answer 6

Closure is a locally declared variable related to a function which stays in memory when the function has returned.

Question 7

What is the difference between .call() and .apply()?

Answer 7

• .call() is used when the number of the function’s arguments are known, as they have to be mentioned as arguments in the call statement
• .apply() is used when the number is not known and expects the arg to be an array

Question 8

What does the array reduce method do?

Answer 8

The reduce() method executes a reducer function (that you provide) on each element of the array, resulting in a single output value.

Question 9

What are the 2 arguments the reduce methods takes?

Answer 9

• Arrow function

- The initial value to start with

Question 10

How does the array filter method work?

Answer 10

- It takes a function and returns a new array of all elements that pass the test in the function. Example:
let arr = [1, 2, 3];
lat newArr = arr.filter(element => {
  return element === 2;
})

Question 11

What is the spread operator and what does it do?

Answer 11

It is 3 dots … and it takes all elements from an array