Interview questions for hiring JavaScript developers

Interview, yes! Whether you are a developer or looking for a JS developer, this information could be helpful for both of you. Check the developer's capabilities who will implement the product by verifying hard skills and identifying whether the specialists can work efficiently with other team members. So, let's examine both parts.

Java Script is a good choice. Did you know that 68% of the top 10k global websites use the three most popular JavaScript (and TypeScript) frameworks, namely, React, Angular, or Vae.js? It'sIt's a 761% growth compared to 2018! But if you are already using JS, you know why you love it - simple, versatile, rich ecosystem, and so on.

With such a popular language on the market, how is it even possible to find the best developers for your business? Or, if you are a developer, you may ask yourself, how could I get the best job offer if I already have all the required skills for the position? Well, the perfect interview could be the answer for both of you. And here are some of the best questions that could be asked in the interview for JS developers.

You can ask JS specialists numerous questions to verify their skills. Each senior specialist or tech lead who will conduct the tech part of the interview has their own approach to interviewing JS programmers and their own list of questions that they think are worth asking. From my work experience, I found 5 of the most interesting questions to ask that tell a lot about hard skills.

Top 5 hard skills interview questions

1. Question: 0.1 + 0.2 = ? Why?
   Expected answer: 0.30000000000000004
   Tricky? Maybe, to keep the post short and engaging, you can read the explanation on the resource if you want.

2. Question: “b” + “a” + +”a” + “a” = ? Why?
   Expected answer: "baNaNa"
   Explanation: JS interpreter tries to coerce the second ""a"" to number (two ""+"" signs before it), which results in NaN.

3. Question: type of NaN
   Expected answer: number
   Explanation: although it says Not a number, NaN is treated as a numeric type.

4. Question: Name a JavaScript String function that modifies the original string.
   Expected answer: there are no such functions.
   Explanation: Strings are immutable in JavaScript, so there are no functions that modify the original string.

5. Question: 1.toString()
   Expected answer: It will throw a SyntaxError.
   Explanation: JS interpreter expects decimal places after the dot but doesn't find any.

However, hard skills are just one constituent that should be verified when you are hiring a JS specialist or applying yourself. Non-technical skills that will show you the ability of the coder to interact with others shouldn't be neglected either.

Soft skills interview

When hiring JavaScript software engineers, it's a must to pay attention to their communication skills and ability to work as a part of the team. It's crucial since JS specialists communicate not only with tech professionals but also with a BA, PM, designers, the client, and other stakeholders.

So, hope you find it helpful. Share the questions that you were asked in the interview, or maybe tell me the questions you like to ask the contender. It would be interesting to read. This post is mainly based on this source and my experience; share your thoughts.