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JavaScript Exercises

Javascript exercises, practice questions and solutions.

If you are a JavaScript learner, then Practice JavaScript Online (JavaScript Exercises) by solving JavaScript quizzes, track progress, and enhance coding skills with our engaging portal. These JavaScript practice questions are ideal for beginners and experienced developers. So, to test your skills, go through these JavaScript exercises with solutions.

A step-by-step JavaScript practice guide for beginner to advanced level.

Benefits of Practice JavaScript

Interactive Quizzes: Engage in hands-on JavaScript quizzes.
Progress Tracking: Monitor your learning journey.
Skill Enhancement: Sharpen coding skills effectively.
Flexible Learning: Practice at your own pace.
Immediate Feedback: Receive instant results and feedback.
Convenient Accessibility: Accessible online, anytime.
Real-world Application: Apply JavaScript concepts practically.
Comprehensive Learning: Cover a range of JavaScript topics.

How to Start Practice ?

Embark on your JavaScript learning journey with our online practice portal. Start by selecting quizzes tailored to your skill level. Engage in hands-on coding exercises, receive real-time feedback, and monitor your progress. With our user-friendly platform, mastering JavaScript becomes an enjoyable and personalized experience. Elevate your coding expertise today.

JavaScript Best Practice Guide

Dive into JavaScript excellence with our Best Practice Guide. Explore coding standards, optimization techniques, and industry-recommended approaches. Elevate your skills through insightful tips, real-world examples, and interactive challenges. Unlock the secrets of efficient and maintainable JavaScript coding, ensuring your projects stand out with clarity and performance.

Why Practice JavaScript Online ?

Elevate your JavaScript online test experience with categorized fill-in-the-blank questions. This structured format guides your learning, providing targeted challenges for hands-on improvement. Engage in focused practice as it reinforce coding concepts, receive instant feedback, and enhance your skills incrementally. Moreover, by combining theoretical understanding with practical application, you’ll enjoy a comprehensive and effective approach to mastering JavaScript and as a result optimizing your performance in real-world scenarios.

JavaScript online practice Rules

Be Honest: Complete challenges independently, refrain from plagiarism or seeking unauthorized help.
Manage Time: Adhere to assessment time limits, simulating real-world scenarios.
Code Quality : Prioritize clean, efficient, and well-documented code.
Follow Guidelines : Adhere to platform-specific instructions, including input/output formats and code submission procedures.
No Cheating: Avoid external resources during assessments, unless explicitly allowed.
Utilize Feedback: Learn from automated or mentor/community feedback.
Participate Actively: Engage in forums, discussions, and share insights with fellow learners.
Continuous Improvement: Use assessments to identify and improve areas of weakness for ongoing growth.

Features of Practice Portal

Instant Mistake Correction: Receive immediate feedback on errors to facilitate quick learning.
Unlimited Tries: Allow learners to attempt questions multiple times for mastery.
Time Display for Each Category: Show elapsed time for each set of 5-6 fill-in-the-blank questions to manage time effectively.
Table View of Scenarios: Provide a comprehensive table view displaying all categories, their status (completed or pending), and corresponding scores.
Performance Analytics: Track progress with detailed analytics, highlighting strengths and areas for improvement.
Interactive Code Editor: Offer a responsive code editor for an immersive hands-on experience.
Hints and Solutions: Include hints for guidance and solutions to foster self-learning.
Community Integration: Facilitate collaboration through forums and discussions for peer learning.
Adaptive Difficulty: Adjust difficulty levels based on user performance for personalized challenges.
Gamification Elements: Incorporate scoring, achievements, or badges to make learning engaging.

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About JavaScript

146 coding exercises for javascript on exercism. from wordy to high score board..

Get better at programming through fun, rewarding coding exercises that test your understanding of concepts with Exercism.

Parse and evaluate simple math word problems returning the answer as an integer.

Nucleotide Count

Given a DNA string, compute how many times each nucleotide occurs in the string.

High Score Board

Practice JavaScript objects by tracking high scores of an arcade game.

Key Features of JavaScript

Runs almost everywhere.

Build web-pages, write backend, create database scripts, make mobile apps, design CLI-s, and more.

Use any programming style

Use prototype-based, object-oriented, functional, or declarative programming styles, and more.

No types required

Dynamically and weakly typed by default, gain typed confidence using Flow, JSDoc, or TypeScript.

Concurrency is safe

Async/await, dedicated workers, or state sync in shared workers. No deadlocks or race conditions.

Largest package registry

No need to reinvent the wheel. Build on top of > 1.3 million packages (April, 2020).

Designed by a committee

Frequent updates, following ECMAScript, a general purpose, cross platform, vendor-neutral standard.

A taste of the concepts you'll cover

Get mentored the javascript way.

Every language has its own way of doing things. JavaScript is no different. Our mentors will help you learn to think like a JavaScript developer and how to write idiomatic code in JavaScript. Once you've solved an exercise, submit it to our volunteer team, and they'll give you hints, ideas, and feedback on how to make it feel more like what you'd normally see in JavaScript - they'll help you discover the things you don't know that you don't know.

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Javascript fundamentals, javascript arrays, javascript objects, javascript dates, javascript sets.

Master .css-8ujquh{background-color:#fdcb6e;color:rgba(0, 0, 0, 0.87);padding:0px 8px;} JavaScript with Open Challenge !

Improve your skills and become a better developer by solving coding exercises online. Whether you're a beginner or an advanced developer, we have exercises for everyone! Join a community of thousands of satisfied people from different countries who are already learning with us!

JavaScript Challenges

Master JavaScript with challenging coding exercises. Improve your skills with practice!

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Learn JavaScript at any level. Our exercises cater to all skill levels. Start growing today!

Practice What Matters to You

Choose from a variety of topics. We believe in engaging, fun learning. Pick your favorite and start practicing!

What sets Open Challenge apart

Whether you're just starting out with JavaScript, or you're already an experienced developer, Open Challenge has everything you need to take your skills to the next level. Our carefully crafted exercises are designed to be both challenging and fun, so you can learn and grow as you practice.

Our platform is built with developers in mind. Our coding challenges are designed to keep you ahead of the curve, and our user-friendly interface makes it easy to navigate and find the topics you're most interested in. Plus, you'll have access to to an assistant with Artificial Intelligence to help you with any queries.

Whether you're a complete beginner or an experienced developer, Open Challenge is the perfect place to level up your JavaScript skills. So what are you waiting for? Start your journey today!

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JavaScript Practice for Beginners: 8 Free JavaScript Exercise Sites

updated Apr 17, 2024

What are the best sites for JavaScript practice for beginners?

Where can you find the best JavaScript exercises and coding challenges?

Whether you are new to coding or have been learning for a while already, you want to have a go-to list of fun JavaScript practice sites to improve your skills continuously.

Because the truth is:

The only way to become a skilled JavaScript developer is to use the language for as many real-world projects as you can.

Sure, you will start small in the beginning. But as your skills progress, you will build more complex projects that require a deeper understanding of the language.

To help you get started, I’ll share my favorite JavaScript practice sites with free and fun JS exercises, challenges, and quizzes in this guide.

By the time you finish reading it, you will have a list of go-to resources to brush up your JavaScript and discover new ways to use the language for real-life projects.

If you truly want to stand out from others and become a professional JavaScript developer, these websites can help you take your skills to the next level.

FYI: I’ve already covered JavaScript projects for beginners in another article . If you haven’t already, definitely check it out, too.

Now let’s get started!

Please note: This post contains affiliate links to products I use and recommend. I may receive a small commission if you purchase through one of my links, at no additional cost to you. Thank you for your support!

What is JavaScript? What can you do with JavaScript?

If you’re not familiar with JavaScript, let’s take a few moments to go through the fundamentals first.

JavaScript is a programming language used for making websites more interactive and dynamic.

What does that mean exactly?

To understand how JavaScript works, you need to know how front-end developers build websites in general .

Here’s a quick overview of the three languages used for creating and building web pages:

HTML or HyperText Markup Language: You can use HTML to create the basic structure and the content for a web page: menu bar, content area, sidebar, bottom footer, etc.
CSS or Cascading Style Sheets: CSS allows you to select individual HTML elements and change their appearance. In other words, CSS makes HTML pretty.
JavaScript : JS takes those static HTML/CSS elements and adds life to them. For example, it allows you to create elements that the user can interact with, such as drop-down menus, contact forms, modal windows, animations, interactive maps, and more.

All in all, JavaScript makes websites more engaging and interesting.

For more details, make sure to read my complete guide on front-end and backend web development .

Free JavaScript practice websites to learn how to code for beginners

Why learn JavaScript?

If you are new to coding and not sure whether JavaScript is the right programming language to learn, don’t worry.

Before you choose your first programming language , make sure you know what you want to create and build with code in the future.

Depending on your specialization, you need to learn a specific set of programming languages and other tools.

Hence, only learn JavaScript if it’s a language you can use for the type of projects you want to work on.

With that said, here are 5 good reasons to learn JavaScript this year:

1: JavaScript is in high demand

If you are serious about becoming a JavaScript developer, you are going to love the fact that JavaScript is one of the most sought-after skills in tech today.

According to the Devskiller IT Skills Report , 75% of companies are looking for JavaScript developers:

The top programming languages companies are looking for – DevSkiller top IT skills report 2021

Furthermore, searching for “JavaScript developer” on the Indeed job portal returns over 20,000 jobs requiring this skill – alone in the US.

2: JavaScript developers are well-paid

So we know that there are plenty of job openings for skilled JavaScript developers. But how much do they make?

According to Indeed, the average base salary for JavaScript developers in the US is $110,687 per year .

You can find out more in this super comprehensive JavaScript salary guide .

JavaScript developer salary in United States April 2024

3: JavaScript is beginner-friendly

If you are new to coding, I recommend picking a language that allows you to focus on learning how coding works and how you can build your own, useful projects asap.

Choosing an easy language means you will spend less time troubleshooting your code and trying to understand the syntax. Thus, you’ll have more time to actually learning how to code.

Luckily, JavaScript is one of the easiest programming languages for beginners .

Now, while the syntax isn’t always the easiest to grasp, you will always find answers to your JavaScript questions thanks to the massive global community of JavaScript experts. This helps you troubleshoot your code faster and makes learning how to code much easier.

4: JavaScript is versatile

JavaScript is an extremely versatile programming language. You can use it for front-end web development to create stunning website interfaces, but also for backend coding using Node.js.

Also, you can develop web apps, mobile apps, and desktop apps using React, React Native, and Electron.

If you want to become a front-end web developer , JavaScript is a must-have skill.

But you could use your JavaScript expertise in the future to work as a full-stack developer, software engineer, or game developer, for example.

Hence, even if you are new to coding and not sure what you want to do in the future, JavaScript doesn’t restrict you to just one area in tech.

5: You can learn JavaScript for free

Last but not least, learning JavaScript doesn’t have to be expensive!

If you are new to coding, I recommend starting with free resources to get a hang of how JavaScript works. You will find tons of ideas in my guide with 100+ free places to learn how to code .

If you enjoy working with the language, consider investing in a paid course that includes as many practical coding projects as possible.

Building small projects and solving coding problems is the only way to improve your skills and learn how to use JavaScript for building real-life projects.

Therefore, you want to pick a course that offers as many portfolio-ready projects as possible , such as these two courses on Udemy:

JavaScript Web Projects: 20 Projects to Build for Your Portfolio You get to build 20 practical portfolio projects throughout the course – even if you are entirely new to programming. That kind of a portfolio is going to look great when you apply for your first entry-level job.
Modern JavaScript From The Beginning Whether you’re a beginner or an established JS developer already, this course has something for everyone. You will build 10 portfolio projects throughout the course, ranging from a simple calculator to more demanding exercises.

For more resources, check out these recommended JavaScript courses and tutorials .

JavaScript Web Projects - 20 Projects to Build Your Portfolio on Udemy

JavaScript practice for beginners: 8 free sites with JavaScript exercises

Here are the 8 top JavaScript practice sites we’ll cover in this post:

Learn JavaScript
freeCodeCamp.org
JavaScript Hero
Learn JavaScript on Codecademy
Khan Academy: JavaScript Quiz

Remember to share and save this guide for later!

1. Edabit JavaScript Challenges

Edabit offers 2,500+ hands-on JavaScript practice challenges ranging from very easy to expert-level tasks.

You can practice directly in your web browser, and all exercises are free.

Creating an account isn’t necessary, but you can track your progress more easily when logged in. Also, you will get access to the solutions for all practice challenges as a registered user.

In addition to JavaScript, you can also find practice exercises for C#, C++, Java, PHP, Python, Ruby, and Swift on Edabit.

Price: Free

Skill level: Beginner to expert

→ Start practising JavaScript with Edabit here

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2. w3resource JavaScript Exercises, Practice, Solution

w3resource’s JavaScript practice directory includes hundreds of free JavaScript challengers ranging from beginner to intermediate in difficulty.

If you are entire new to coding, make sure you are somewhat familiar with JavaScript and its syntax before these exercises.

One of the best places to learn JavaScript is freeCodeCamp.org , for example. Their courses are 100% free and you can start learning in 2 minutes.

w3resource also offers free tutorials for other popular technologies, such as:

Responsive web design

Skill level: Beginner to intermediate

→ Start practising JavaScript with w3resource here

3. Learn JavaScript

If you are looking for a complete online course with beginner-level JavaScript practice exercises, Learn JavaScript is definitely worth checking out.

Their JavaScript course covers the fundamentals of the syntax, giving you a solid foundation for practising your skills while building real-life projects as you go.

Learn JavaScript – JavaScript coding exercises for beginners

The lessons are to the point, fluff-free, and you will get a quick recap after each module to support your learning.

You can practice JavaScript directly in your web browser, solving interactive challenges and building meaningful coding projects.

Price: Free trial, Pro plan unlocks all content

→ Start practising JavaScript with Learn JavaScript here

4. W3Schools JavaScript Exercises

W3Schools is one of the best places to find free JavaScript exercises and practice challenges.

If you are entirely new to JavaScript, start learning with their free JS tutorial for absolute beginners . You will go through quick lessons to learn the syntax and apply what you learn right away to hands-on coding exercises and quizzes.

If you are new to coding, W3Schools also offers free tutorials in other popular languages like:

→ Start practising JavaScript with W3Schools here

5. freeCodeCamp.org

freeCodeCamp is one of the best websites to learn to code from scratch, and they offer a ton of free JavaScript practice material ranging from beginner to intermediate level skills.

freeCodeCamp JavaScript practice challenges and exercises

The freeCodeCamp curriculum starts with HTML and CSS, after which you will start learning and practising JavaScript.

Hence, if you are new to programming, remember that you need to learn at least some HTML and CSS before tackling JavaScript. That’s another reason why freeCodeCamp is a fantastic place to start. You can learn everything in one place – for 100% free.

→ Start practising JavaScript with freeCodeCamp here

6. JavaScript Hero

JavaScript Hero is a simple but effective JavaScript practice platform for beginners. You will start with the basics and learn how variables, functions, parameters, and other syntax fundamentals work.

Each lesson includes a quick exercise based on what you just learned. If you run into difficulties, you’ll find a helpful hint for each exercise. Also, JavaScript Hero provides a solution for all lessons and practice challenges.

→ Start practising JavaScript with JavaScript hero here

7. Codecademy: Learn JavaScript

Learn JavaScript is Code c ademy’s free JavaScript course for beginners. Although the course is free per se, you only get access to a limited number of JavaScript exercises, practice challenges, and projects. If you are new to coding, this is more than enough to get started.

And don’t forget to grab your free JavaScript cheatsheet on Codecademy, too.

Learn JavaScript – Free JavaScript course on Codecademy

If you enjoy learning with Codecademy, you can unlock the entire course catalog with hundreds of real-life projects with the Pro plan .

Codecademy Pro also gives you unlimited access to the Front-End Engineer career path that teaches you everything you need to know to create beautiful web experiences and start a career as a front-end developer.

If you aren’t familiar with them, you can learn more in my complete Codecademy review .

Price: Free (with limited content), Pro plans start at $19.99 when paid annually

Skill-level: Beginner to intermediate

→ Start practising JavaScript with Codecademy here

8. Khan Academy: JavaScript Quiz

Khan Academy is a free online course platform for popular topics such as computer programming , math, economics, and science. Although a lot of their content is aimed at kids and students, it’s perfectly suited for any age.

Their free Intro to JavaScript course teaches you JS from the ground up, even if you are completely new to tech. You will learn about variables, data types, functions, conditionals, loops, and more.

After the course, you can finish a set of JavaScript practice challenges to test your skills.

→ Start practising JavaScript with Khan Academy here

FAQ: JavaScript practice exercises

Some of the best places to practice JavaScript include Edabit , w3resource , freeCodecamp.org , Codecademy , and W3Schools . They all offer free JavaScript exercises and coding challengers for beginner and intermediate skill levels.

The best way to practice JavaScript is to learn the theory and syntax first. As you go, practice your skills with simple exercises, and start building more complex projects as your skills improve. The concepts build on top of each other. Thus, make sure you feel comfortable with a given topic before moving on to the next one.

If you are new to JavaScript, the easiest way to practice is to take breaks from following tutorials. Take notes of what you learn and try to solve small coding problems with JavaScript on your own without referring to your course or tutorial. Hence, start very small and only proceed to the next topic once you feel comfortable with what you just learned.

You can learn how JavaScript works in 1 week, yes. You may feel comfortable enough to solve small, simple coding problems with JavaScript after a few days of learning the syntax. But it takes much longer to become job-ready and to launch a career as a JavaScript developer. Hence, one week is enough to get an understanding of whether you enjoy working with JavaScript and if you want to continue learning more about it.

In theory you can, yes, but it wouldn’t make much sense. JavaScript is so closely intertwined with HTML and CSS that you shouldn’t learn just one of them. Remember, JavaScript is used to make static websites more dynamic, interactive, and engaging. Without HTML and CSS, you won’t have anything on your website to apply JavaScript to.

Whether you learn Java or JavaScript depends on what you want to build with code in the future. If you want to become a front-end web developer and create gorgeous websites, JavaScript is a must-have tool in your skillset. Java is used for back-end (server-side) development. Thus, if you are more interested back-end programming and want to build desktop apps or Android mobile apps, for example, Java can be a valuable skill on the job market.

I have written a separate article with the best JavaScript project ideas with source code – check it out!

What you need to start practising JavaScript

1. code editor.

I recommend installing a code editor on your computer, although you can use online code editors, too.

Here are a few free code editors you may want to try out:

Sublime Text

For more options, check out my article with the best text editors for coding and web development .

2. Web browser

Since JavaScript runs directly in your web browser, you can simply write your code and instantly test it in your browser.

Make sure you use a modern web browser such as Google Chrome or Mozilla Firefox. You need good developer tools so that you can check the console for any errors in your code and debug them.

3. JavaScript tutorials and courses

If you are new to JavaScript, I recommend trying a few different resources to learn how the language works.

We all have different learning styles, and it’s important that you find out how you learn best.

If video tutorials are easier to follow than going through a physical book, be mindful of that and use materials that support your learning.

I’ve listed some of my recommended JavaScript courses here .

For even more resources, check out these top web development courses , too.

4. JavaScript syntax cheatsheet

Wrapping your head around the syntax can be tricky in the beginning. Using a cheatsheet is a quick way to save time when you need a quick refresher or want to double-check something.

I love this free JavaScript cheatsheet on Codecademy. For a compact PDF version, check out this free JS cheatsheet .

5. Portfolio for your JavaScript projects

As you work through your JavaScript practices and your skills improve, you will start building more complex JavaScript projects.

To showcase your skills and best work samples to potential employers, you want to set up a professional-looking portfolio website. It doesn’t have to be anything too fancy – a simple one-page website is more than enough to get started.

Keep your design clean and clear, and don’t be afraid to show some personality!

To help you get started, I’ve written a free step-by-step guide for creating a portfolio website from scratch .

Summing it up: Where to find the best JavaScript exercises and practice projects

This article showed you a handful of great JavaScript practice sites for improving your coding skills at your own pace.

I hope you found a few helpful resources for beginner-friendly and fun JavaScript exercises and coding challenges!

So the question is: what are you going to build first? Please share your thoughts in the comments below!

If you need some help with your JavaScript practice projects, check out these top JavaScript and jQuery courses and tutorials .

For my proven learning strategy, check out the best way to learn JavaScript from scratch .

Make sure to bookmark this article and share it with others, too. Thank you for your support!

Free JavaScript practice websites for beginners

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About mikke.

Hi, I’m Mikke! I’m a blogger, freelance web developer, and online business nerd. Join me here on MikkeGoes.com to learn how to code for free , build a professional portfolio website , launch a tech side hustle , and make money coding . When I’m not blogging, you will find me sipping strong coffee and biking around town in Berlin. Learn how I taught myself tech skills and became a web dev entrepreneur here . And come say hi on Twitter !

List of Problems

This page contains the list of all programming problems in no particular order. If you have solved a problem, its row turns green. Click on any problem to start coding!

DEV Community

Posted on May 9, 2020

FREE PDF: 50 JavaScript Coding Challenges for Absolute Beginners

Hi Dev.To Community,

I'm sharing a PDF with 50 JavaScript coding challenges (and their solutions). All solutions are presented in classic JavaScript syntax in order to appeal to beginners.

Advanced users can have fun too!

Download link: https://codeguppy.com/site/download/50_coding_challenges.pdf

Happy coding!

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Location Sussex, England
Education YouTube, Udemy, freecodecamp
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Solve common problems in your JavaScript code

The following links point to solutions to common problems you may encounter when writing JavaScript.

Common beginner's mistakes

Correct spelling and casing.

If your code doesn't work and/or the browser complains that something is undefined, check that you've spelt all your variable names, function names, etc. correctly.

Some common built-in browser functions that cause problems are:

Semicolon position

You need to make sure you don't place any semicolons incorrectly. For example:

There are a number of things that can go wrong with functions.

One of the most common errors is to declare the function, but not call it anywhere. For example:

This code won't do anything unless you call it with the following statement:

Function scope

Remember that functions have their own scope — you can't access a variable value set inside a function from outside the function, unless you declared the variable globally (i.e. not inside any functions), or return the value from the function.

Running code after a return statement

Remember also that when you return from a function, the JavaScript interpreter exits the function — no code after the return statement will run.

In fact, some browsers (like Firefox) will give you an error message in the developer console if you have code after a return statement. Firefox gives you "unreachable code after return statement".

Object notation versus normal assignment

When you assign something normally in JavaScript, you use a single equals sign, e.g.:

With Objects , however, you need to take care to use the correct syntax. The object must be surrounded by curly braces, member names must be separated from their values using colons, and members must be separated by commas. For example:

Basic definitions

What is JavaScript?
What is a variable?
What are strings?
What is an array?
What is a loop?
What is a function?
What is an event?
What is an object?
What is JSON?
What is a web API?
What is the DOM?

Basic use cases

How do you add JavaScript to your page?
How do you add comments to JavaScript code?
How do you declare a variable?
How do you initialize a variable with a value?
How do you update a variable's value? (also see Assignment operators )
What data types can values have in JavaScript?
What does 'loosely typed' mean?
What types of number do you have to deal with in web development?
How do you do basic math in JavaScript?
What is operator precedence, and how is it handled in JavaScript?
How do you increment and decrement values in JavaScript?
How do you compare values in JavaScript? (e.g. to see which one is bigger, or to see if one value is equal to another).
How do you create a string in JavaScript?
Do you have to use single quotes or double quotes?
How do you escape characters in strings?
How do you join strings together?
Can you join strings and numbers together?
How do you find the length of a string?
How do you find what character is at a certain position in a string?
How do you find and extract a specific substring from a string?
How do you change the case of a string?
How do you replace one specific substring with another?
How do you create an array?
How do you access and modify the items in an array? (this includes multidimensional arrays)
How do you find the length of an array?
How do you add items to an array?
How do you remove items from an array?
How do you split a string into array items, or join array items into a string?

Debugging JavaScript

What are the basic types of error?
What are browser developer tools, and how do you access them?
How do you log a value to the JavaScript console?
How do you use breakpoints and other JavaScript debugging features?

For more information on JavaScript debugging, see Handling common JavaScript problems . Also, see Other common errors for a description of common errors.

Making decisions in code

How do you execute different blocks of code, depending on a variable's value or other condition?
How do you use if ...else statements?
How do you nest one decision block inside another?
How do you use AND, OR, and NOT operators in JavaScript?
How do you conveniently handle a large number of choices for one condition?
How do you use a ternary operator to make a quick choice between two options based on a true or false test?

Looping/iteration

How do you run the same bit of code over and over again?
How do you exit a loop before the end if a certain condition is met?
How do you skip to the next iteration of a loop if a certain condition is met?
How do you use while and do...while loops?

Intermediate use cases

How do you find functions in the browser?
What is the difference between a function and a method?
How do you create your own functions?
How do you run (call, or invoke) a function?
What is an anonymous function?
How do you specify parameters (or arguments) when invoking a function?
What is function scope?
What are return values, and how do you use them?
How do you create an object?
What is dot notation?
What is bracket notation?
How do you get and set the methods and properties of an object?
What is this , in the context of an object?
What is object-oriented programming?
What are constructors and instances, and how do you create them?
What different ways are there to create objects in JavaScript?
How do you structure JSON data, and read it from JavaScript?
How can you load a JSON file into a page?
How do you convert a JSON object to a text string, and back again?
What are event handlers and how do you use them?
What are inline event handlers?
What does the addEventListener() function do, and how do you use it?
Which mechanism should I use to add event code to my web pages?
What are event objects, and how do you use them?
How do you prevent default event behavior?
How do events fire on nested elements? (event propagation, also related — event bubbling and capturing)
What is event delegation, and how does it work?

Object-oriented JavaScript

What are object prototypes?
What is the constructor property, and how can you use it?
How do you add methods to the constructor?
How do you create a new constructor that inherits its members from a parent constructor?
When should you use inheritance in JavaScript?
How do you manipulate the DOM (e.g. adding or removing elements) using JavaScript?

Practice Problem Lists

Collection of all practice problem lists on codedamn

100 Days of Frontend
30 Days of HTML CSS
30 Days of Java
30 Days of Python
30 Days of React
30 Days of Solidity
50 Days of JavaScript
50 Days of SQL
Basic Web Development
DSA Practice Problems
Frontend Interview Questions
Hacktoberfest 2023
Java Practice Problems
JavaScript Logic Building
Python Practice Problems
React.js Problems
Top Node.js Questions

JavaScript Coding Interview Practice – Sample Interview Questions and Solutions

David Goggins is an ultramarathon runner, a public speaker, a retired navy SEAL, and the author of the book ' Can't Hurt Me: Master Your Mind and Defy the Odds '. He's one of my role models because of his physical strength and mental resilience.

You might say: "Wait a second! We get it. This person is obviously the epitome of success. But he has non-technical skills. So why is he relevant to JavaScript coding interviews?"

Well, if you're ready, let's explore this together.

Rocky Balboa As a Mentor

In response to a question, David says, 'The Rocky Movie changed my life." In that pep talk , he refers to this scene (min 1.30-1.42) where the fictional character, Rocky - despite being beaten up badly by his opponent in the final boxing round - refuses to give up no matter what.

David describes that particular moment as the time when Rocky - initially depicted as an underdog by the screenwriter - overcomes all the odds and strikes awe in his rival.

Let's admit it. Being a good programmer is not that easy. And especially if you are at the beginning of your career, technical job interviews can be seriously daunting. In short, it might be nice to reach David's (and Rocky's) mindset.

With that kind of drive and confidence, you're much less likely to consider giving up regardless of the types of challenges you face in your wonderful yet difficult journey of getting a developer job.

Why Coding Interviews Are Difficult

During coding interviews, you are expected to fix coding problems with some theoretical knowledge. But the caveat is you must do that in real time, which sometimes scares new developers off.

There are several types of coding interviews. But the most challenging one is probably a whiteboard interview. In these types of interviews, you have to code in front of a future employer / a senior software developer.

These interviews can be extra stressful because you are typically not allowed to have a computer to google any unknown concepts or to get some code snippets from the internet. You are only given a marker to solve the question on a whiteboard as the name suggests.

Do Interviews Reflect What You'll Do in Your Job?

Not necessarily. So why are they holding these scary coding interviews? Well, the reason is to test your problem solving skills in general. At times, finding the correct answer may not even be that important.

What matters is how you reach that conclusion / solution and which algorithms you prefer to use along the way. In other words, your ability to function well under stress is being tested by tech companies.

Let's face it. You'll come across lots of stressful situations in your future job, and how you deal with certain issues is especially crucial. Therefore, your future employer naturally wants to witness firsthand whether you are the right fit for the job.

What is the Purpose of This Tutorial?

In this post, I'll walk you through some popular JavaScript interview concepts through examples. I'll also do my best to show you what recruiters / interviewers might actually be looking for in a candidate while they code in front of them.

To simply put, we'll examine some models and try to solve the related puzzles together.

By the end of this tutorial, you'll hopefully have an idea about a number of important array methods. But most importantly, you'll unlock how to approach some coding challenges in the best way possible.

What Exactly is the Memory Palace Method?

Before we start, just be aware that in the sample data down below, I've used some late celebrities' names intentionally so that all those details can be catchy in the long run.

An ancient technique called the Memory Palace clearly says that the weirder the details, the easier it is to remember them – and a made-up story / creating context is even more effective.

If you try to visualise the related situation vividly and associate the given programming concepts with some bizarre details in your mind, you might feel less stressed and confused when you see a similar problem next time. This is because it might be easier for you to create specific links and as such remember things easily. This is how our brains work.

Well, even the fictional figure ' Sherlock Holmes ', the smartest guy on the planet, benefits from this method when solving complicated crimes – so why shouldn't we?

How to Approach Coding Problems

In our imaginary interview, you'll see that four extraordinary musicians from the past are listed as passengers on a flight. We have their food choices and the number of connecting flights they need to take after their incredible performances on stage in different parts of the world.

Let's say just for the sake of argument our phenomenal figures (Freddie Mercury, Amy Winehouse, Kurt Cobain, and Michael Jackson) are about to fly from different destinations to Los Angeles just to be able to dine out together at a swanky restaurant, as they enjoy each other's company so much.

After all, this is our own private memory palace, so we can absolutely do whatever we want to do in our minds. Remember unusual details will stick better. That's why I'm trying to add more to spice things up.

This method explicitly suggests describing every single detail with some vivid adjectives so that you can associate them with the things you plan to learn in the long run.

Scientists say short term memory and long term memory function very differently. To put it simply, we need a way to put all those core concepts (not necessarily the syntax) about programming in our long term memory. That's why it can be nice to benefit from the memory palace method in our journey.

Plus, I feel like you get to picture this unusual scenario with a smile on your face. Well, wouldn't it be great if these awesome souls could have seen that they are now helping us / the programming community as the guests of a freeCodeCamp article?

Sample Interview Questions

Let's get back to the real life now though. Remember you're still in the interview and as you see below, three questions in a row are waiting for you.

To solve the puzzles, you're expected to use the data inside the following array of objects in practical ways.

You'll certainly need to come up with the right algorithms and try to find the most effective solution that can satisfy the interviewer.

The above questions are in fact not that hard. But, how we'll handle them is a great opportunity to compare alternative solutions for a single problem. At the end of the day, quality is what counts for recruiters / interviewers.

Interview Question 1: How to Get Passengers' Names

Let's get the passengers' names as requested. The first solution is through a 'for loop' method. So we first need to use an empty array to push the passengers' names right inside it at the end of the loop.

Below, [i] represents the current passenger and we simply loop through the 'passengers' array to access the names of the passengers. Then, we need to lock them up in our empty array / passengerNames.

Alright, we solved the puzzle, but is it enough? Or might the interviewers expect you to come up with a better solution?

Alternative Solution #1:

We can reach the desired result by using the ' forEach ' function as well. This solution is even a bit better than the previous one because there is no index expression in this one.

To benefit from 'forEach', we need a callback function . With this arrangement, we are able to reach every passenger in the list. However, just like in the previous solution, we first need an empty array to push the items / passengers' names.

Even though the result is the same, this piece of code is shorter. Writing neater codes is what is – in fact – expected from you.

In other words, not only the solution matters, but also how you reach it is being evaluated by the recruiters. For this reason, it is a good idea to plan your action rather than writing the first idea in your mind on the whiteboard.

Alternative Solution 2:

Here comes the best solution. We can also utilise the ' map ' function to tackle the same problem. Let's see how.

The map function also loops through the array and returns a new array for every item in the list. With this set-up, we simply return a single element, not an object.

The result will again be the same in the console, but your code will even be better than the first and second one because this time, we don't need to create an empty array before the actual task.

Here is the food for thought on this topic. Those who say 'less is more' have a point when it comes to writing codes.

Interview Question 2: How to Get Vegetarian/Vegan Singers

Let's now take a look at the next challenge. The new task asks us to obtain only the vegetarian / vegan singers from the passengers' list by also keeping the first argument in the main question section.

How to Solve With a 'For Loop'

Again, we can use the same old 'for loop' for this one as well. All we need to do is to check whether there are any vegetarian / vegan singers in our passenger list through an 'if' statement inside our existing function.

We do that with the isVegetarianOrVegan property in our object. Basically, what we say is this: if the relevant statement is true (if there are any vegan / vegetarian passengers in the list), just push those items into our new array. The result will give us three singers' names as those are listed as 'vegetarian or vegan' in the data part.

How to Solve with 'forEach'

As a matter of fact, the 'forEach' function handles the problem similarly. But once again, it has too many lines of codes as you see below, so it isn't the ideal version.

How to Solve with 'Filter' & 'Map'

To come up with the best option, this time, we will use two different methods. The ' filter ' and the 'map' functions will – in a way – collaborate to create better logic when solving the given problem. Let's examine the following code snippet closely now.

With the filter method, we only get the vegetarian / vegan passengers from our array in the first place. If it finds some non-vegetarian / vegan passengers (like our beloved 'Freddie'), it will get rid of them automatically.

Briefly, the first part of the equation, the 'filter' method will simply work through 'yes' or 'no' model.

Then, the 'map' function will come in, eventually giving us a brand new array showing the vegetarian / vegan passengers only.

This final solution will prove your future employer that you genuinely know what you're doing and you are really taking the right steps to be a hotshot developer.

Interview Question #3: How to Sort Passengers by Connecting Flights

The last section asks us to sort the list of our super cool passengers by the number of the connecting flights they'll take to eventually reach LA. Let's see who has more and as such, will be pretty exhausted.

Spoiler alert! Amy with four connecting flights in total might be a bit sleepy in the get-together at that fancy restaurant. But there is no doubt that she will somehow rock where ever she goes.

Anyway, what we need for this task is to know how the ' sort ' function operates.

Primarily, it compares items one by one and returns something as a result. In our case, it will be the number of connected flights. But how does it make that comparison? What is the logic behind that?

The above lines of code are pretty clear in general. Thanks to the 'sort' function, we list those months in alphabetical order.

Well, here comes the big question. How does the code / system know that 'a' is the first letter of the alphabet and as such, the list starts with the 'd' letter (December)?

The reason is that the 'sort function' lists things in ascending order by default. But can't we change this setting? Perhaps, we need to list items in descending order. Of course, we can.

Let's see how. To achieve what we want, we may utilise 'a' and 'b' letters as parameters leading to different directions.

Simultaneously, we can benefit from the assistance of three numbers: -1,+1, 0 as seen above. When sorting items in descending or ascending order or finding the equal values, they can be quite handy.

Tricky Bit of the 'Sort' Function

In the following example, the list is sorted in ascending order. Why is it like that? Here is the reason. When we return those 'a' and 'b' parameters, we use this order: 'a - b' . That gives us ascending values by default.

However, if we swap them and say 'b - a', the list will be seen in descending order this time. That's the tricky bit when it comes to the 'sort' function.

In the above example, the first version (regular function) and the second one (arrow function) are in essence the same, but just be aware that arrow functions came with ES6 .

Although arrow functions help developers to write less code, you cannot use them everywhere. (Read this to find out when to use them.)

Testing Our New Knowledge

Shall we now analyse the situation of our passengers through our new perspective? We know that the last task asks us to sort the number of flights in descending order. But the following set-up does the opposite.

It can only give us the list in ascending order. Why? It's simply because of the pre-defined order (passenger1.connectedFlights - passenger2.connectedFlights) as in the case of a - b example.

Once we swap the order (passenger2.connectedFlights - passenger1.connectedFlights) as you see in the following code snippet, our problem will be solved and the list will come in descending order.

Can We Also Use 'for loop' or 'forEach'?

Well, yes and no. Both would be low-level solutions for this question.

We should keep in mind that the sort function mutates an array. This is a kind of side effect which changes the original array and that might be a problem if we use 'for loop' or 'forEach' as a solution.

There are of course ways to avoid mutation in the sort function, but in our example, it will lead to more lines of codes, which is not practical at all.

Wrapping Up

We've started the article with David Goggins, the symbol of resilience and grit, so let's end it with his inspiring presence and ideas.

If you happen to read this modern day hero's book or listen to one of those famous podcast episodes (For example, this one ) where he was a guest speaker, you'll immediately understand that he wasn't born that way. Rather, his secret lies in the fact that he never gives up, against all odds.

Coding interviews are tough, but if you keep going after your goals by visualising the scene of success in your mind over and over again, it will - sooner or later - be yours.

Many thanks for reading this post. If you've liked this article, one of the best ways to support me is to share it. Should you have any questions or comments, you can always contact me via LinkedIn . I'll be more than happy to help you out with your queries.