21 Node.js Interview Questions with Solutions


21 Node.js Interview Questions for Landing Your Next Job

Preparing for a job interview is always a daunting task. Most likely you don’t know exactly what you’ll be asked and nerves can easily take over, making you forget even your own name. I’ve compiled 21 Node.js questions for job interviews that go from very simple stuff to some more technically advanced topics to help you in the process.

Node.js is not exclusively used in the back end. We also use it to create front-end applications, and this has become a very important part of the Web Development ecosystem. This means that it’s very useful for a Node.js developer to be familiar with the role this technology plays in different JavaScript environments. For this reason, I’ve included some questions and answers along those lines.

Guidelines

I would recommend trying to answer the questions yourself before reading the answers. If you didn’t get them all, try again tomorrow to see how much you’ve retained.

There’s also the chance you’re here looking for interview question examples for your candidates. I believe these should be varied enough as a starting point to help you assess their level.

More than just answering a question correctly, I think it’s the details that show how much someone knows. A good answer might ignite a conversation that could potentially render a stressful experience into a casual chat with a colleague. That’s an ideal result for both parties.

Node.js Questions

What is Node.js?

Node.js is a JavaScript runtime environment based on the V8 engine. It allows us to run JavaScript outside of the browser — typically, in a web server.

What is Node.js good for?

Node.js is great at handling multiple connections with low cyclomatic complexity, given that its single-threaded nature requires that we liberate the event loop as soon as possible. This makes Node.js an ideal choice for microservices and real-time applications.

What is npm?

npm stands for Node.js Package Manager. It consists of a command-line interface that we can use to access an online registry of public and private packages.

How do you create a Node.js app from scratch?

We can start by creating a project folder. Then, we navigate to that folder in the command line and run npm init. Finally, we follow the steps to fill our app information.

What does “npm install” do?

It installs the dependencies found in the package.json file.

How do you install a library in Node.js?

npm install name-of-the-library will install our library and include it as a dependency. If we add the --save-dev parameter it will be included as a devDependency.

How do you create a custom script?

We need to go into the package.json and add our custom script within the scripts field. We can then run our script by going to the terminal and running npm run name-of-script.

Is it possible to create a front-end application with Node.js?

The browser can’t run a Node.js application, but you could use something like webpack or Parcel to bundle the code and turn it into something a browser could run. It’s very common nowadays to use a Node.js environment for building front-end applications. A good example of Node.js in the front end is the Electron framework, which makes use of both Node.js and chromium to build “native” apps like, for instance, VS Code.

Can you mention three popular Node.js frameworks?

Express.js is probably the most popular framework to date. Koajs is probably one of the fastest and Sails.js works great for real-time bilateral communication apps given that use socket.io.

What is Express.js good for?

Express.js makes it dead easy to set routes for our web app, which makes it an obvious choice to create REST APIs. It’s quite flexible and easy to use, and its middleware architecture helps to keep a simple and scalable system.

What is Crypto?

Crypto is a Node.js internal library that provides cryptographic functionality to do things like, for example, encrypting and decrypting passwords.

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