Node.JS Mock Interview | Interview Questions for Senior Node.JS Developers

As a senior Node.JS developer, it’s important to be well-prepared for job interviews. One way to ensure success is to participate in mock interviews and practice answering common interview questions. In this article, we will discuss some key interview questions commonly asked for senior Node.JS developer positions.

1. Explain what Node.JS is and its key features.

Node.JS is a powerful, open-source, server-side JavaScript runtime environment. It allows developers to build scalable and high-performance web applications. Some of its key features are:

• Non-blocking I/O model
• Event-driven architecture
• Single-threaded but highly scalable
• Ability to handle concurrent requests efficiently

2. Differentiate between readFile and createReadStream in Node.JS.

The readFile function is used to read the entire contents of a file into memory before processing. On the other hand, createReadStream is used to read large files in chunks, making it more memory-efficient. createReadStream is preferred for processing large files or when dealing with streaming data.

3. Explain the concept of middleware in Node.JS.

In Node.JS, middleware is a function that has access to the request and response objects in the application’s request-response cycle. It can modify the request/response objects, execute code, or pass control to the next middleware function. Middleware is used to add functionality to an application, handle error handling, authentication, parsing request bodies, etc.

4. How does Node.JS handle asynchronous code?

Node.JS uses the event-driven, non-blocking I/O model to handle asynchronous code. It employs callback functions, promises, or async/await to manage the asynchronous flow. This allows Node.JS to handle multiple concurrent requests efficiently and avoid blocking the event loop.

5. What is the purpose of the package.json file in a Node.JS project?

The package.json file is a manifest file that contains metadata about a Node.JS project and its dependencies. It includes details such as the project name, version, author, scripts, dependencies, and more. It allows developers to manage project dependencies, define custom scripts, and provide information for other developers working on the project.

6. Explain the concept of event-driven programming in Node.JS.

Event-driven programming in Node.JS is based on the observer design pattern. It revolves around the idea of events being raised and handled by event emitters. Event emitters emit events when certain actions or conditions occur in an application. Developers can register event listeners to handle these events and execute specific code.

7. How does Node.JS handle modules?

Node.JS uses the CommonJS module system to handle modules. Modules in Node.JS are encapsulated pieces of code that can be reused across multiple files. They can export functions, objects, or variables using the module.exports syntax. Other files can then import and use these modules using the require function.

8. What are streams in Node.JS?

Streams in Node.JS are used to handle continuous data flows. They provide an interface for reading from or writing to a source sequentially. There are different types of streams, including readable, writable, and duplex streams. Streams allow data to be processed in chunks, reducing memory usage and improving application performance.

9. Describe error handling in Node.JS.

Error handling in Node.JS can be done through try-catch blocks or by using callback functions or promises with the error as the first argument. Node.JS provides a built-in error class called Error for handling and throwing errors. Additionally, developers can use the process.on('uncaughtException') event to catch unhandled exceptions and avoid application crashes.

10. What is clustering in Node.JS?

Clustering in Node.JS enables the creation of multiple Node.JS processes to handle incoming requests. It takes advantage of multi-core systems, distributing the workload across multiple CPUs to improve application performance and scalability.

These are just a few of the many possible questions a senior Node.JS developer might encounter during a job interview. It’s important to study the concepts, practice coding, and gain hands-on experience with Node.JS to confidently answer these questions and impress potential employers.