Top Node JS Senior Developer Interview Questions to Practice

Node.js is an open-source, cross-platform, single-threaded, backend JavaScript runtime environment and library. Node.js executes the JavaScript code outside the client’s web browser and runs on the V8 engine. Since Node.js is single-threaded, it’s mainly used for non-blocking, event-driven servers. 

We can use Node.js to create server-side data-intensive applications due to its asynchronous and event-driven model. We can also use it for developing distributed systems, general-purpose, real-time, and network applications. This article focuses on senior Node JS developer interview questions to help you prepare. 

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In this article, we’ll cover:

• Node JS Senior Developer Interview Questions and Answers
• Advanced Node JS Interview Questions for Senior Developers
• Node JS Senior Developer Interview Questions for Practice
• FAQs on Node JS Senior Developer Interview Questions

Node JS Senior Developer Interview Questions and Answers

We’ll begin with some basic Senior Node JS Developer interview questions and answers to get an idea of what to expect.

1. How does Node.js handle child threads?

Node.js indeed spawns child threads for some tasks like asynchronous I/O. However, they run behind the scenes without executing any JavaScript code in the application and without blocking the main event loop. 

Node.js is a single-threaded process. It does not expose thread management methods and child threads to the developer. Tools enable threading support in a Node.js application like the ChildProcess module. Node.js 12 also offers experimental support for threads.

2. What is the control flow function, and what does control flow do?

The control flow function is a function, a block of code, that runs in between several asynchronous function calls. The control flow controls the order of execution, collects information, limits concurrency, and calls the next step in a program.

3. How is Node.js most frequently used?

We use Node.js most frequently in IoT, Complex SPAs, real-time chats, real-time collaboration tools, microservices architecture, and streaming applications.

4. Name the two types of API functions in Node.js.

Asynchronous, non-blocking, and synchronous blocking functions are the two types of API functions in Node.js.

5. List the various Node.js timing features

setTimeout or clearTimeout, setInterval or clearInterval, and setImmediate or clearImmediate are three functions provided by the Timers module for executing code after a specific period.

Sample Node JS Senior Developer Interview Questions

Now, here are some sample Senior Node JS Developer interview questions. See if you can solve them:

1. Define and describe the usage of the following:

• Node.js
• Event Emitter
• Error-first callback
• Callback hell
• WASI
• Reactor pattern in Node.js
• Buffer class in Node.js
• Timing features of Node.js
• Test pyramid in Node.js
• Package.json file
• Reactor Pattern in Node.js
• Event Loop
• Global installation of dependencies
• NODE_ENV
• LTS releases of Node.js
• Piping in Node.js
• Streams in Node.js
• Middleware
• The module .Exports
• Express.js package
• REPL

Advanced Node JS Interview Questions for Senior Developers

Let’s move a step further with some Senior Node JS Developer interview questions for experienced professionals:

1. How does Node prevent blocking code?
2. Why does Google use the V8 engine for Node.js?
3. How does Node.js handle concurrency given it’s single-threaded?
4. How does Node.js support multi-processor platforms?
5. Does Node.js fully utilize all processor resources? If yes, how?
6. Why do we need to separate the Express app and server?
7. Talk about the modules in Node.js.
8. What is usually the first argument passed to a Node.js callback handler?
9. Explain config file separation for dev and prod environments via an example.
10. What is the purpose of REPL?
11. Name some tools that help ensure consistent code style.
12. Explain callback hell along with ways to avoid it.
13. What are the advantages of Node.js?
14. What are the disadvantages of Node.js?
15. Why is Node.js preferred over Java, PHP, and other backend technologies?
16. Explain the various types of HTTP requests.
17. State the advantages of using promises overusing callbacks.

Node JS Senior Developer Interview Questions for Practice

Lastly, here are some technical Senior Node JS Developer interview questions. Ensure you can solve them before your interview:

1. Name and explain some of the flags used in the read/write operations in files.
2. How would you create a simple Express.js application?
3. Talk a bit about asynchronous, non-blocking APIs in Node.js.
4. Name the command used to import external libraries.
5. How would you install, update, and delete a dependency?
6. Describe how to use a URL module in Node.js.
7. How would you create a simple server in Node.js that returns Hello World?
8. Name some of the most commonly used libraries in Node.js.
9. Differentiate between process.nextTick() and setImmediate().
10. Differentiate between fork() and spawn() methods in Node.js.
11. Differentiate between Angular and Node.js.
12. What method is preferred for resolving unhandled exceptions in Node.js?
13. How would you implement async in Node.js?

FAQs on Node JS Senior Developer Interview Questions

Q1. What should a senior Node.js developer know?

A senior Node.js developer should have experience in front-end design and development using HTML and CSS. A senior Node.js developer is also expected to know crucial JavaScript concepts and have error-handling skills. They should also have the necessary skills associated with RESTful APIs and API communications. 

Q2. Name a database that’s popularly used with Node.js.

MongoDB is a cross-platform, NoSQL, document-oriented database most commonly used with Node.js. Its advantages include high availability, high performance, and ease of scalability.

Q3. Why is Node.js Single-threaded? Is Node.js synchronous or asynchronous?

Node.js is asynchronous and is single-threaded to enable async processing. Async processing on a single thread under usual web loads allows us to achieve more performance and scalability than the general thread-based implementation.

Q4. What is REPL in Node.js?

REPL refers to Read, Eval, Print, and Loop in Node.js.

Q5. Why should we use Node.js?

Node.js is fast, asynchronous, rarely blocks, yields great concurrency, offers a unified language and data type, and eases the process of building scalable network programs.

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