JavaScript Interview Questions - Coding Interview 2025 from Udemy

This course is great preparation for any javascript programming interviews that you may have coming up. Programming interviews need a lot amount of knowledge, but the best way to prepare for interviews is a lot of practice. In this course you will complete 59 javascript interview questions that come from real javascript interviews. There are no excersises that nobody asks here. In every question we will get a task first, then you will try to solve each problem yourself, and then I will show you different solutions to each problem step-by-step for different programmer levels. We will take a deep dive into the skills, concepts, and techniques that are required to solve each problem.

When you have completed this course you will have mastered the 59 interview questions that we will cover, but you will also have learned the concepts, skills, and techniques, that are necessary for you to excel in any other interview questions you may be asked. You will feel very confident going into any javascript programming interviews you will have. On top of all this, you will strengthen your javascript programming skills and javascript fundamentals in overall.

Core topics of the course:

Closures
Hoisting
Currying
Classes & Prototypes
Modules
Working with DOM
Asyncronous Javascript (Callback, Promises, Async await)
Memoization
Transforming data with real world tasks
Creating own utility functions

What's inside

Learning objectives

Be very well prepared for any javascript programming interviews you will have
Excel in a wide variety of javascript interview questions that you could be asked in an interview
Strengthen you javascript programming skills and your knowledge of important javascript concepts

Learn the skills, concepts, and techniques necessary to excel in javascript coding interviews
Learn what programming interviews are like and what kind of questions to expect
Feel very confident going into any javascript programming interviews you will have

Be very well prepared for any javascript programming interviews you will have
Excel in a wide variety of javascript interview questions that you could be asked in an interview
Strengthen you javascript programming skills and your knowledge of important javascript concepts
Learn the skills, concepts, and techniques necessary to excel in javascript coding interviews
Learn what programming interviews are like and what kind of questions to expect
Feel very confident going into any javascript programming interviews you will have

Syllabus

Core Javascript Concepts

What is this section about?

Types of Interviews

Interview and Work Are Completely Different Things

Pdf file

I prepared source code for you

Mapping Users to Get Usernames

Difference between null and undefined

Hoisting

Closures

Currying

Adding Elements to the Array

Concatenating Arrays

Check if User With Such Name Exists

Remove All Duplicates in the Array

Sorting the array

Interview Is Not What You Think

Writing Range Function

Writing Shuffle Function

Find the Number of Occurences of Minimum Value in List

This

Classes

Prototypes

I’ve Failed Interview. What’s Next?

Modules

Implement Debounce Function

Implement Throttle Function

Working with DOM

Highlight All Words Over 8 Chars With Yellow

Add a Link

Split Each Sentence to a Separate Line

Event Delegation

Asynchronous Javascript

Xml HTTP Request

Fetch API

Basic Callback

Parallel Async Array

Convert Callback to Promise

Map Data in Promises

Rewrite Mapping Data in Async Await

You Must Use Correct Vocabulary

Design Request Manager

Comparison Functions

Implement Shallow Comparison

Implement Deep comparison

Create Memoization Function

Tasks Asked Only on Interview

Fibonacci

Palindrome

Anagram

Finding vowels

Tasks From Every Day Work

Convert to Title Case

Convert the Time Input Given in 12 Hours Format to 24

Mapping Data

Replace Parameters in URL

Validation Messages

Nested List

What's next?

Homework

My Bonus Lecture

Good to know

Know what's good

, what to watch for

, and possible dealbreakers

Offers practice with 59 JavaScript interview questions, providing hands-on experience that is invaluable for interview preparation

Covers core JavaScript concepts like closures, hoisting, and asynchronous JavaScript, which are frequently tested in coding interviews

Includes topics like working with the DOM, which is essential for front-end developers and often appears in interview questions

Explores techniques for transforming data and creating utility functions, skills that are highly applicable to real-world JavaScript development tasks

Includes 'Tasks Asked Only on Interview,' which may not be directly applicable to real-world projects, but are useful for interview preparation

Features a section on XMLHttpRequest, which is an older technology that has largely been replaced by Fetch API for asynchronous requests

Activities

Be better prepared before your course. Deepen your understanding during and after it. Supplement your coursework and achieve mastery of the topics covered in JavaScript Interview Questions - Coding Interview 2025 with these activities:

Review JavaScript Fundamentals

Show steps

Solidify your understanding of core JavaScript concepts before diving into interview questions. This will make it easier to grasp the solutions and techniques presented in the course.

Browse courses on JavaScript Fundamentals

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Review data types, variables, and operators.
Practice writing basic functions and control flow statements.
Familiarize yourself with the DOM and event handling.

Read 'Eloquent JavaScript'

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Expand your knowledge of JavaScript by reading 'Eloquent JavaScript'. This book provides a deeper understanding of the language and its features.

View Eloquent JavaScript, 4th Edition on Amazon

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Read the book cover to cover, paying close attention to the examples.
Complete the exercises at the end of each chapter.
Experiment with the code examples and try to modify them.

LeetCode Easy JavaScript Problems

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Practice solving easy JavaScript problems on LeetCode to build your problem-solving skills. This will help you approach interview questions with more confidence.

Show steps

Create a LeetCode account and familiarize yourself with the platform.
Filter problems by difficulty (Easy) and language (JavaScript).
Solve at least 5-10 problems per week, focusing on different data structures and algorithms.

Four other activities

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Show all seven activities

Read 'You Don't Know JS' series

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Deepen your understanding of advanced JavaScript concepts by reading the 'You Don't Know JS' series. This will help you answer more complex interview questions.

View You Don't Know JS Yet: Get Started on Amazon

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Choose one or two books from the series that cover topics you want to learn more about.
Read the books carefully and take notes.
Try to apply the concepts you learn to your own projects.

Create a JavaScript Interview Cheatsheet

Show steps

Compile a cheatsheet of common JavaScript interview questions and their solutions. This will serve as a valuable reference during your interview preparation.

Show steps

Review the interview questions covered in the course.
Summarize the key concepts and techniques required to solve each question.
Organize the information in a clear and concise format.
Include code snippets and examples to illustrate the solutions.

Mock JavaScript Interviews

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Practice answering JavaScript interview questions with a peer. This will help you identify your strengths and weaknesses and improve your communication skills.

Show steps

Find a partner who is also preparing for JavaScript interviews.
Take turns asking each other interview questions.
Provide constructive feedback on each other's answers.
Focus on both technical accuracy and communication skills.

Contribute to an Open Source JavaScript Project

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Gain practical experience by contributing to an open-source JavaScript project. This will demonstrate your skills and knowledge to potential employers.

Show steps

Find an open-source JavaScript project that interests you.
Read the project's documentation and contribution guidelines.
Identify a bug or feature that you can work on.
Submit a pull request with your changes.

Career center

Learners who complete JavaScript Interview Questions - Coding Interview 2025 will develop knowledge and skills that may be useful to these careers:

JavaScript Developer

A Javascript developer works primarily with Javascript to build interactive websites and applications. This course provides very focused training in Javascript by working through difficult code problems. It covers core Javascript concepts like closures, prototypes, and asynchronous Javascript. A Javascript developer would greatly benefit from using this course to improve their skills. The course's approach of presenting a problem, attempting a solution, and then reviewing different solutions is excellent preparation for the kind of thought process used by a Javascript developer. This course helps increase an individual's confidence in coding.

See salaries and explore the career path for JavaScript Developer

Frontend Engineer

A frontend engineer creates user interfaces for websites and applications, using languages like Javascript. This course directly helps a prospective frontend engineer through its focus on Javascript, a core technology for the role, and its focus on practical coding questions. The course's in-depth exploration of Javascript concepts like closures, hoisting, and asynchronous operations, as well as DOM manipulation, are skills that a frontend engineer will rely on daily. By practicing real interview questions, this course prepares an individual for the technical evaluations often required during the hiring process for a frontend engineer. This course helps build a strong foundation for any kind of coding challenge that might be faced in the role.

See salaries and explore the career path for Frontend Engineer

Software Developer

Software developers are involved in various aspects of software creation, including both client-side and server-side logic, and often work in multiple languages. This course provides a focused and high-intensity path to improve one's proficiency in Javascript, an extremely important language for web development. The course covers essential Javascript concepts like closures, classes, and asynchronous programming. The interview preparation aspect directly translates to improved problem-solving and code-writing skills, which are critical for anyone wishing to work as a software developer. The practice with real interview questions also provides a great opportunity to sharpen code writing skills.

See salaries and explore the career path for Software Developer

Web Developer

A web developer builds websites, and they require a strong grasp of Javascript, HTML, and CSS. The Javascript concepts covered in this course such as asynchronous programming and working with the DOM, are directly relevant to a web developer's daily tasks. The course's practice with interview-style problems helps sharpen a web developer's coding skills and problem-solving abilities. The course provides targeted preparation for the kinds of coding challenges a web developer might encounter in both the interview process and on the job. This course strengthens important programming fundamentals needed for the role of a web developer.

See salaries and explore the career path for Web Developer

Software Engineer

Software engineers design, develop, and maintain software systems, and they must bring a strong foundation in programming principles and languages. This course in Javascript interview questions is helpful in solidifying Javascript skills and preparing for technical interviews. A software engineer regularly needs to solve coding problems, and the practice in this course will help to improve these skills, especially when it comes to the Javascript language. The course's detailed explanation of coding techniques and Javascript concepts helps any prospective software engineer prepare for both the interview process and the challenges of the job itself. The course provides targeted practice to help prepare for coding challenges.

See salaries and explore the career path for Software Engineer

Full-Stack Developer

Full stack developers work on both the frontend and backend of software applications, requiring expertise in many technologies, including Javascript. This course offers a focused way to enhance Javascript skills, which are essential for client-side development and, increasingly, server-side development using Node.js. The course's deep dive into Javascript concepts and its focus on tackling real interview questions directly benefits a full stack developer by improving their coding proficiency and problem-solving abilities. Aspiring full stack developers will find the emphasis on core Javascript concepts to be particularly useful. The course helps prepare one for the technical challenges of the role of full stack developer.

See salaries and explore the career path for Full-Stack Developer

UI Engineer

A user interface engineer focuses on the visual and interactive aspects of software. For this role a deep understanding of Javascript is very helpful. This course helps a UI engineer by providing focused training in Javascript, which is used to implement user interaction. The course directly improves skills in areas like DOM manipulation and asynchronous programming, which are crucial for creating responsive user interfaces. Interview preparation strengthens problem solving abilities. The course may help one feel more prepared for the technical aspects of being a UI engineer.

See salaries and explore the career path for UI Engineer

Application Developer

An application developer is responsible for creating software applications for various platforms, and will likely use Javascript in part of that process. This course provides essential Javascript training through solving difficult, real-world coding problems. The course's coverage of asynchronous Javascript, DOM manipulation, and core language concepts directly assists an application developer. The interview-focused exercises also help a prospective application developer in the interview process, offering a practical way to build confidence and skill. This course helps prepare someone to code with confidence.

See salaries and explore the career path for Application Developer

Backend Developer

Backend developers focus on the server-side logic and databases that power applications. While backend development may not always require Javascript, it is increasingly common, especially with Node.js usage. This course may help a backend developer by strengthening his or her Javascript abilities for tasks that require it. The course's focus on core language concepts, asynchronous operations, and problem-solving can be beneficial in certain backend development contexts. The course can be helpful in broadening technical knowledge.

See salaries and explore the career path for Backend Developer

Mobile Developer

Mobile developers create applications for mobile devices, and they often use Javascript to some extent, especially if they are using frameworks like React Native or Ionic. This course may be useful to a mobile developer, as it helps to solidify Javascript skills through interview-style coding problems. The course's focus on fundamental Javascript concepts and asynchronous programming may especially help those who use Javascript for mobile development. By learning practical problem-solving skills, this course may prepare someone for the challenges of mobile development.

See salaries and explore the career path for Mobile Developer

Game Developer

Game developers create video games using various technologies and languages, and Javascript might be used for web-based games or game user interfaces. This course may help a game developer who uses Javascript by improving their core language abilities. The course's focus on problem solving, and Javascript concepts strengthens a game developer's coding knowledge. The course may also enhance confidence in one's coding skills and may be useful in the interview process as well.

See salaries and explore the career path for Game Developer

Data Scientist

Data scientists analyze large datasets to uncover insights, and they may occasionally use Javascript for data visualization tools. While Javascript is not the core language of data science, this course may help a data scientist who needs to work with Javascript. The course provides a focused way to learn Javascript, enhancing skills needed for web based data visualization. This course may add a practical skill to a data scientist's skill set.

See salaries and explore the career path for Data Scientist

Technical Consultant

A technical consultant advises clients on technology solutions and might require some familiarity with Javascript. This course may be useful for a technical consultant to gain Javascript proficiency or solidify knowledge. The course helps to improve coding abilities, which will be useful in discussions and project work. The course may provide a deeper understanding of developer-level work.

See salaries and explore the career path for Technical Consultant

Technical Writer

Technical writers create documentation for software and technology and sometimes need to understand code, including Javascript. This course may be helpful for a technical writer to gain a practical understanding of the language and improve their ability to document code effectively. The course provides a great opportunity to see real Javascript being written, which is useful for a technical writer in their work. The course may help build confidence in this area.

See salaries and explore the career path for Technical Writer

Quality Assurance Engineer

Quality assurance engineers test software for defects, and they might need some familiarity with Javascript for testing web applications. The coding skills taught in this course may provide a quality assurance engineer with a better understanding of how code is built and tested. The course may also be helpful for creating and reviewing test scripts. The course may be a useful way to gain knowledge of how software is built using Javascript and how to test it.

See salaries and explore the career path for Quality Assurance Engineer

JavaScript Interview Questions - Coding Interview 2025

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