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15 JavaScript Interview Questions to Ask Your Potential Developer

Do you want to hire a superb JavaScript developer? JavaScript is the most popular scripting language today to build apps and websites,...

JavaScript Interview Questions

Do you want to hire a superb JavaScript developer?

JavaScript is the most popular scripting language today to build apps and websites, as per talent acquisition platform Reintech. As a result, countless businesses are looking for JavaScript programmers to join their teams. It provides entrepreneurs a way to build quality products and compete in the market for more shares.

However, you must conduct an interview and ask the right questions to ensure you have the right person. Here are the top JavaScript interview questions to ask your candidate to understand if they fit your role.

JavaScript Interview Questions to Assess Tech Skills

You need sound tech skills to build top-notch apps and websites. Your developer, too, should have enough technical prowess to ensure your project’s success.

Warm-up your candidate with the introductory questions below and then move towards more technical questions.

1. General Interview Questions for JavaScript Developers

What is your most exciting JavaScript project? Share your experience and insights.

This question provides your candidate the opportunity to highlight their best JavaScript skills. Additionally, they can share what they learned from the project that might be useful for your role.

2. What is your favorite JavaScript development stack?

Coders use a range of JavaScript frameworks and tools to develop efficiently. This question allows recruiters to find out how familiar the candidate is with current technology. Plus, you also get to know if the person will be able to use the resources planned for your project.

3. What is the most significant technical challenge you have encountered? How did you resolve the issue?

The question above lets you gauge how good your candidate is at solving problems. They should be able to explain the solution they took in technical terms clearly.

For example, I used a test-driven development approach to resolve the challenge of bugs in apps.

JavaScript Interview Questions to Evaluate Hard Skills

Now comes the turn to assess your candidate for tech skills. Ask the questions below to find out if your potential developer is right for your job title:

4. Why do businesses prefer JavaScript over other scripting languages?

JavaScript has a few unique benefits that make it a top choice for development. This question lets you find out how well your candidate knows JavaScript and its applications.

What to look for:

The interviewee should be able to spell out the technical aspects that make JavaScript popular. For example, they may say JavaScript supports functional programing to simplify development.

Vague answers like, “JavaScript is easy to learn” show the candidate lacks solid tech skills.

5. Name the data types in JavaScript.

This is a question to test the foundational understanding of JavaScript. It has around seven data types, so your candidate should be able to name at least five or six.

Probable answers:

  • Number
  • Boolean
  • Undefined
  • Object
  • Symbol

6. What are the few factors you will look out for while reviewing someone else’s code?

Junior coders can make many mistakes while coding. However, an experienced JavaScript programmer knows these beginner mistakes and how to avoid them.

What to look for:

Your interviewee should be able to name factors like readability, functionality, and more. Security is also a top aspect to review while evaluating code.

7. How can you test JavaScript code automatically? Will you use any tools?

Testing is an integral part of JavaScript development. Any developer you hire should know all types of testing to develop apps without bugs.

What to look for:

Your potential developer should name different testing methods like unit testing and functional testing. Additionally, they should spell out the names of a few testing tools like Ava or Phantom.

8. How long have you been using JavaScript? What types of apps did you make?

This is a classic question to evaluate the experience of your candidate. You also get to know the different types of projects they worked in to assess their exposure.

As a result, you can determine if the candidate is the right fit for your project.

9. How do you ensure the app you develop is a delight to use?

JavaScript is a front-end language that lets businesses deliver excellent user experiences. Your potential developer should absolutely be able to create a seamless UI and foster user-friendliness.

What to look for:

Your candidate should clearly state the steps they take to ensure a top user experience. They may name approaches like testing across devices or lazy loading to make apps user-friendly.

Plus, they should be able to achieve accessibility and usability standards.

10. How would you eliminate errors from web applications?

Bugs are expected in apps. However, a JavaScript developer will be extra careful to ensure their code is free of errors.

This question lets you understand the approach your candidate will take to reduce bugs. Additionally, it can throw more light on their debugging skills.

You should also ask your interviewee to name a few debugging tools.

11. What is the role of the isNaN() function in JavaScript?

The isNaN() function helps determine if a value is an illegal number or not a number. It is one of the many small things in JavaScript that comes in handy during development.

A candidate who can answer this question knows the ins and outs of JavaScript and all its aspects.

Create a sample development project or use one of your old ones. Then ask your candidate what tool would be the best for the purpose.

The question reveals if your interviewee takes the time to understand the requirements of a project. It can also give an insight into how they go about coding.

In addition, you can also find out about their knowledge of different tools.

JavaScript Interview Questions to Assess Soft and Behavioral Skills

A few personal traits and behaviors can make your developer the ideal person for your team. As a result, you should always ask questions to determine soft skills when you hire a JavaScript developer.

12. What steps do you follow to focus on your work at hand?

Developers need to juggle multiple tasks and workflows at once. Therefore, they should be able to concentrate and work methodically to complete your project. The answer to this question will help you find out if your interviewee is one of them.

13. Share an experience where you had a conflict with a team member. How did you resolve it?

This question allows you to understand how easy or difficult it is to work with the candidate. Plus, it can throw more light on their team spirit.

14. Are you planning to learn any new technology in the recent future?

Developers should stay updated on the latest technologies. Plus, they should be keen to learn new things to make better contributions.

Ask this question to understand if your candidate is passionate about his work.

Final Thoughts

The answers that your candidate gives you help you determine their skills. You can also have a technical person in your team to handle the tech round of your interview. Plus, you can create more questions based on our examples to suit your project.

Additionally, conduct tasks like coding tests and pair programming to assess your candidate thoroughly. You should also evaluate soft skills properly if you want the right person for your needs.


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Written by Liza Katiushchenko
Digital Marketing and Social Media Manager at Reintech.

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