Node JS Developer Interview Questions
In the world of server-side development, Node.js has emerged as a leading contender, enabling fast, scalable network applications. To find the adept talent that can harness its asynchronous, event-driven architecture, this article curates a set of thoughtful interview questions. Dive in to discern a candidate's expertise in creating efficient backend systems using JavaScript and Node.js.
What is Node.js?
Answer: Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine, designed to build scalable network applications.
2.
Why is Node.js single-threaded?
Answer: Node.js uses a single-threaded event loop to handle asynchronous tasks, which allows it to manage high concurrency without multi-threading.
3.
Explain the difference between async and await in Node.js.
Answer: async declares a function as asynchronous, while await is used inside an async function to wait for a Promise to be resolved or rejected.
4.
What is the Event Loop in Node.js?
Answer: The Event Loop handles the execution of multiple chunks of your code over time, managing the callback queue and system events.
5.
What is npm?
Answer: npm (Node Package Manager) is a package manager for JavaScript, primarily used to install and manage software libraries in Node.js.
6.
How do you handle exceptions in Node.js?
Answer: Exceptions can be handled using try...catch blocks, and with process.on('uncaughtException', callback) for uncaught exceptions.
7.
Describe the difference between exports and module.exports in Node.js.
Answer: While both are used to export modules, module.exports is the actual object that gets exported. exports is just a reference to module.exports.
8.
What is the use of a buffer in Node.js?
Answer: A buffer is a temporary storage location for raw data, allowing you to manipulate, store, and transfer data to/from streams, file systems, and sockets.
9.
Explain the concept of middleware in Express.js.
Answer: Middleware functions have access to the request and response objects and the next middleware function. They can execute any code, make modifications to the request and response, or end the request-response cycle.
10.
What is the difference between setImmediate() and process.nextTick()?
Answer: process.nextTick() defers the execution of a function until the current event loop has completed, while setImmediate() defers it to the next iteration of the event loop.
11.
What is a Promise in Node.js?
Answer: A Promise represents a value which might be available now, or in the future, or never. It provides a way to handle asynchronous operations' success or failure.
12.
How do you create a RESTful API using Node.js?
Answer: You can use frameworks like Express.js to create routes, handle HTTP methods (GET, POST, PUT, DELETE), and send responses to create a RESTful API.
13.
Describe the purpose of package.json.
Answer: package.json holds metadata about a project, such as its dependencies, scripts, and version. It serves as a manifest for projects in Node.js.
14.
What are event emitters in Node.js?
Answer: Event emitters provide a mechanism to raise and handle custom events in Node.js. The events module provides the EventEmitter class.
15.
What are streams in Node.js? Name some types.
Answer: Streams handle streaming data. They can read or write data in chunks, improving performance. Types include Readable, Writable, Duplex, and Transform streams.
16.
What's the difference between dependencies and devDependencies in package.json?
Answer: dependencies are required for the application to run, while devDependencies are only required during development, like testing libraries.
17.
How do you handle file uploads in Node.js?
Answer: One can use middleware like multer with Express.js to handle multipart/form-data, which is used for file uploads.
18.
What is REPL in Node.js?
Answer: REPL stands for Read-Eval-Print-Loop. It's an interactive shell for executing JavaScript code.
19.
How do you debug a Node.js application?
Answer: You can use the built-in debugger, Node Inspector, or tools like Visual Studio Code's debugging capabilities.
20.
What is the Cluster module in Node.js?
Answer: The Cluster module allows forking multiple child processes (workers) that run simultaneously, improving performance and load balancing.
21.
What's the role of a callback function in Node.js?
Answer: Callbacks are functions passed as arguments and are executed after the completion of an asynchronous operation.
22.
How can you prevent callback hell in Node.js?
Answer: By using modern ES6/ES7 features like Promises, async/await, or generators, or utility modules like async.
23.
What is the purpose of __dirname and __filename?
Answer: __dirname returns the directory name of the current module, and __filename returns the file name of the current module.
24.
How do you secure your Node.js applications?
Answer: Use HTTPS, validate and sanitize input, set HTTP headers appropriately, handle errors without revealing internals, and use security middleware like helmet.
25.
Explain the role of the request and response objects in Express.js.
Answer: The request object represents the incoming HTTP request, containing data like headers and query parameters. The response object is used to send back data and headers to the client.
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