JavaScript Developer Interview Questions | 2022

JavaScript Developer Interview Questions | 2022


Whether you’re interviewing for your first JavaScript developer job or your 15th, preparation will make all the difference in getting hired and earning your salary expectations. It’s a competitive market out there, but with the right interview questions and answers, you can catch the attention of potential employers and secure your next position as an elite JavaScript developer in 2022!

Questions to Ask JavaScript Developers During Interviews

Here are some of the questions that you can ask a JavaScript developer during interviews.

What are the major advantages of JavaScript?

The major advantages of JavaScript are that it's a widely used programming language, it's cross-platform compatible, and it has an abundance of libraries. These features make JavaScript a popular choice for web development because you can use the same language on both the client and server sides. This also means that you don't have to spend time or money translating from one programming language to another when switching from back-end to front-end development or vice versa.

Explain Hoisting in javascript.

Hoisting is a JavaScript term that means functions and variables are hoisted to the top of the current scope. This can lead to some interesting behavior when you attempt to call a function or access a variable before it has been declared.

Difference between “ == “ and “ === “ operators.

In JavaScript, the == operator is used to test if two values are equal. The === operator is used to test if two values are strictly equal; which means that they need to be of the same type and have the same value. For example, 10 == 10 evaluates as true but 10 === 10 evaluates as false because they are not strictly equal.

What are the data types supported by JavaScript?

Data types supported by JavaScript are strings, numbers, booleans, undefined values, null values, and objects. The string data type represents text while the number data type can represent integers or floating point numbers. Boolean values represent true or false values where undefined is a special value that indicates that a variable has not been assigned a value yet.

Define some of the most prevalent JavaScript operators.

Operators are symbols that tell the computer what to do with the data you give it. For example, if you want to multiply two numbers together, you can use a multiplication operator: *. The list below includes some of the most common JavaScript operators. ++ and -- are both used for incrementing or decrementing a number by 1. They're called unary operators because only one operand is used.

What’s the difference between JavaScript and Java?

Java and JavaScript are both programming languages, but they serve different purposes. JavaScript is primarily used to create interactive elements on websites like buttons, menus, sliders, etc., while Java is used for more complex projects involving software applications or web services.

What are the advantages of JavaScript over other web technologies?

JavaScript is the most used web programming language. It has many advantages over other languages such as C++ and Java. JavaScript does not need to be compiled, which means that it can run in real-time on the user's browser, enabling a more interactive experience. Furthermore, JavaScript has a number of frameworks and libraries that allow developers to use it for creating single-page applications (SPA). These frameworks include AngularJS and ReactJS.

How do you debug JavaScript code?

One of the most common ways to debug JavaScript code is to use console.log() in order to output the value of an object or variable at a given point in your code. This will let you know what value is being stored for a particular variable and when it changes. You can also take advantage of alerts() and confirm().

What are Imports and Exports in JavaScript?

Most of the time, JavaScript imports are used to import other scripts into your own. Imports allow you to use code from another file without having to copy and paste it. For example, let's say that you want to use a function called Math in your script. To do this, you will need to import the Math script into your script first. This is how:

import {Math} from ./math.js // or import {Math} from math-lib

What is the difference between var and let?

The var keyword declares a variable and is scoped to the function in which it's declared. The let keyword also declares a variable, but its scope is limited to the block of code where it's used.

Why should we use ES6 classes?

ES6 classes are a great way to inherit from another ES6 class. They also allow for private methods in your class, which is not possible in ES5. As JavaScript becomes more and more popular, it is important that developers stay on top of the latest changes to help them create better programs.  

What is the Temporal Dead Zone in ES6?

The TDZ is a period of time after an event has occurred and before it has been observed where code accessing the event may not be able to rely on its value. For example, if you have a variable that tracks whether or not a user is logged in, any code referencing this variable will throw an error if the user logs in right after the page loads because, at the time of loading, that variable was undefined. 

NaN property in JavaScript

NaN is a type of data in JavaScript which means not a number. It is used to represent any numeric value that does not represent a number. In other words, NaN represents an undefined or unknown value.


To recap, I've outlined the most common JavaScript developer interview questions and provided some insight into what you should expect when you're on the hot seat. In many cases, the best way to answer these questions is by using your past experience to draw parallels between the question being asked and a time when you solved a similar problem. Also, remember that it's alright if you don't know an answer right away. That's why they're interviewing you!


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