Guide to JavaScript Interviewing

It’s the 21st century and web users expect full-featured, responsive web applications with intuitive interfaces.

JavaScript helps you create such web applications.

But how?

Generally, great products are made of good code and good code is written by good developers.

So, one sure way to create a great product is to hire a good developer.

However, identifying a good developer amongst a pool of job applicants can be taxing.

Whether you’re looking to hire a front-end designer, a node.js back-end engineer or a full-stack JavaScript generalist, this guide contains interview techniques that can help you do just that.

Good coding relies on more than just the knowledge of a language syntax. You need someone who can turn your wildest dreams into reality, bring new ideas to the table and create stuff people love.

How can you tell this about a stranger by spending 20-30 minutes with them in a conference room or on Skype?

1. Explore their JavaScript Expertise

Rather than testing the applicant’s general coding knowledge, you should focus on their JavaScript chops.

This helps you judge their abilities.

Here’s a quick way to explore:

Ask a simple JavaScript-related question.

Based on the answer, ask a slightly more detailed one, and continue digging in until you reach the candidate’s limit.

Nevertheless, if an applicant has good general experience beyond JS, that’s even better.

2. Get Them to Critique Something

After testing their JavaScript expertise, go a step further to get them to review something—especially a JavaScript-based technology.

Here, you should look to see if:

They get the method signature right

Their algorithm is reasonable

They can explain its workings

They can give some pointers for improvement

They can find common line-break issues and so on.

3. Ask Them to Perform a Quick Task

But when doing this, be careful. The task shouldn’t necessarily be about solving some puzzles or problems.

It’s better to judge using functional code as opposed to abstract modular puzzles with no connection to the actual job in question.

The task should be simple, but practicable in relation to the job.

Whatever it is, don’t ask the candidate to write a code on paper or whiteboard.

The traditional whiteboard coding exercise is a poor indicator of actual coding prowess and a terrible strategy for recruiting devs.

People don’t write code on paper or whiteboard, they do it with computers using macros, context-sensitive help, auto-completion, and indexed API documentation.

If you think it’ll take time for candidates to create something during the interview, then it might make sense to ask them to do so before the interview and bring the code on a notebook PC.

But even then, do not rely totally on the code example. Instead, follow point #4 below to boot.

4. Ask to See Their Work

Most applicants will come prepared for point #3 above—performing a quick task.

And if you base your final judgment on how awesome they were at that, you might end up hiring an incompetent developer.

So before or after the interview, take a few moments to look into the candidate’s code portfolio. It could be open-source or hobby projects.

Review and discuss the design, coding style, and decisions that went into it.

If you like the projects, ask the specific features and functionalities the applicant created.

For example, did the person create the product from scratch or started working on existing code?

Looking at actual code tells you much more than having candidates write rushed-over, contrived five-liners they already crammed.

It tells if someone is good realistically, and not just at the interview.

Wrapping up

To wrap up, here are a few hints to help you even more:

To identify a good JavaScript developer, you have to know JavaScript yourself and know what questions to ask. Otherwise, you won’t understand what applicants present and may end up embarrassing yourself. I recommend getting help from someone who knows JavaScript.

Developers aren’t all the same. A reasonable question depends on the candidate’s expertness.

Discourse is important. So, find a way to engage a conversation.

Finally, the developer’s personality is just as important as their professionalism, because one bad dude can destroy an entire team forever.

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Check out how a few of our Javascript programmers have grown recently.

  • Andrew Stratu
  • Andrew Stratu
  • completed "Advanced SVG Animation" course on
  • attended SmashingConf in Barcelona with 15 other X-Teamers.
  • read "SurviveJS - React", a top resource on mastering React.
  • Gianluca Esposito
  • Gianluca Esposito
  • completed "Building React Applications with Idiomatic Redux" course on Egghead.
  • attended ReactEurope in Paris with 10 other X-Teamers.
  • submitted a pull request to GatsbyJS, a React static site generator.
  • Szymon Michalak
  • Szymon Michalak
  • completed the Webpack course on Egghead.
  • attended SmashingConf in Barcelona with 15 other X-Teamers.
  • read "SurviveJS - React", a top resource on mastering React.


X-Team is a development company that’s spent the last decade building a community of motivated Javascript programmers, architects and consultants from around the world. Today, we provide our developers (individually or as a team) to companies that need help scaling, outsourcing their software projects or leading their development teams with top Javascript developers.


They really care about their developers and I could tell that from the very beginning. I feel like X-Team shows a lot of love and, in turn, that gets brought back to our company as well.

— Danielle Chircop, Kaplan Inc.

What makes X-Team's Javascript developers unique?


The success of any team or product is incredibly dependent on how good their communication is. Without communication that is frequent and consistent, while also setting (and resetting) the right expectations, deadlines simply don't get hit.

We recognize this and have set communication as a priority with our developers. We use a decade's worth of knowledge and remote development techniques that we've created to master this skill.

Here's what it can be like when you hire Javascript engineers from a marketplace site:

Compared to what it's like working with an X-Team Javascript developer:


With a language as popular as Javascript, it's quite common to find Javascript programmers who are either poorly trained or have become comfortable and are no longer motivated to keep growing their skills.

A comfortable Javascript developer is one who probably hasn't learned much about new back-end or front-end frameworks, like Symfony & Laravel in PHP or Angular & React in JavaScript. They also likely haven't made an attempt to become an expert at Docker or AWS to improve their devops skills.

X-Teamers are different, as X-Team's Javascript developers make an effort to keep themselves motivated and always finding ways to learn and grow. We only hire people who have proven they share this same attitude.

We also have a team of Unleashers who are dedicated to individually helping each of our Javascript experts continue to unleash their potential by keeping them motivated like a personal trainer.

We build true partnerships.

Not only are we obsessed with the success and growth of our Javascript programmers, we're also dedicated to the success of our partners.

That's why at X-Team we build partnerships with our clients, a relationship that ensures we are always available to help you scale your team of Javascript developers and ensure their success.

All of our partners have dedicated account managers whose sole purpose is to work with you every step of the way. The level of attention we give to both our partners and our developers is unparalleled in our market and is something we're proud of.


I'd use X-Team again in a heartbeat.— Harper Reed, Threadless

The right team. Kaplan Inc. explains why they chose X-Team. Watch Video

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