Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine, used for building fast and scalable network applications. It is getting more popular day by day.
Because many developers are looking to work with Node.js, it's important to know those particular Node.js interview questions if you're applying for a job requiring this technical knowledge.
Most interview questions have the same format—tell me about your strengths, weaknesses, etc. But in a technical interview, you may be asked questions seemingly out of the box or focused more on that technology.
This blog attempts to list down a few questions specifically in Node.js and how you can approach them.
Node.js is a platform built on Chrome's JavaScript runtime for easily building fast, scalable network applications.
Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across distributed devices.
Node.js allows you to write highly scalable network applications, as it efficiently handles connections with web clients and is also lightweight and fast. Developers use Node.js to build and deploy web applications, network tools, and utilities that run on the server side.
The I/O model in Node.js is a non-blocking event loop. This means that when you call a function that performs I/O, it will not block the execution of your code. Instead, it will return immediately and lets you continue executing other parts of your code while the I/O operation is performed in the background.
The non-blocking nature of Node makes it great for handling high volumes of requests because it can handle multiple requests at once without ever blocking any single request from completion.
The key features of Node.js are:
There are a lot of frameworks and libraries available for Node.js. Some popular ones are:
We can think of functions as variables. This concept is called "first-class functions." Many programming languages follow this pattern, including JavaScript, Scala, Haskell, etc. First class functions are regular, run-of-the-mill functions stored in variables, passed as arguments, or returned from other functions.
There are four layers to a web application:
NPM is Node Package Manager. It's a command line tool that helps you install, share, and manage JavaScript packages for your development workflow. It is pre-installed with Node.js and can be used in the command line interface (CLI) or with any text editor or IDE that supports it.
NPM uses a package.json file to store information about the project, including its dependencies. Because NPM is so popular and widely used, more than 1.3 million packages are available on the registry.
The require() function is used to import external libraries in Node.js. It can be used to import JavaScript files, local modules, or remote modules.
For example, loading the HTTP library can be done by using the required keyword and specifying the HTTP library. This will give you access to the single exported object from the HTTP library through the HTTP variable.
Node.js is a single-threaded application using all CPU cores to process requests. Node.js uses an event loop model to handle requests and events in your application. The event loop is a central component of Node.js and the heart of how Node.js works with I/O operations and the OS kernel.
In event-driven programming, the program waits for a specific event to occur. A simple example of event-driven programming is a calculator application. The calculator doesn't do anything until you press a button or key.
Event-driven programs are usually easier to write and debug than multi-threaded programs because there are fewer places for bugs to hide. They are well suited for applications that need to react quickly to user input.
A callback is a way for a program to call another function or method and pass some data along. It's an important concept in Node because it allows you to write code in one place and execute that same code in another. This helps keep your code modular and reusable, a crucial part of good software engineering.
Callback shells are a common problem in JavaScript applications. This is where you have multiple asynchronous operations simultaneously, each calling another function when done. This can lead to situations where you have a long chain of functions being called before any value is returned.
The first step to avoiding callback hell is to reduce the number of asynchronous operations required in your application. If this isn't possible, try using promise libraries such as Bluebird or Q. These allow you to write code that will be executed once all the asynchronous operations have been completed.
In Node.js, a package is a directory with a file named package.json. This file contains metadata about the package, such as its name, version, author, and dependencies. This allows you to use npm as a dependency manager for your projects and share code with others by publishing packages to the registry.
There are two ways to export an object in Node.js:
Module.exports - This is used for exporting a module so it can be imported into other modules or scripts.
Exports - This is used for exporting a single object from a module so it can be used directly in the main script file.
Middleware functions are functions that receive the request and response objects, as well as the next function in the request-response cycle. The next function is a function in the Express router that, when called upon, will execute the middleware following the current middleware.
REPL stands for Read-Evaluate-Print-Loop. It is a feature of Node.js that allows you to type in JavaScript code and see the result immediately. It is useful when developing or debugging code but is not a substitute for testing.
Control flow functions are pieces of code that help manage the order of execution for async function calls. They ensure that the right data is collected and that concurrency is limited when necessary.
Yes, Node.js has a simple TCP protocol and comes with a debugging client. If you want to debug your JavaScript file, you can use the debug argument and then use the name of the JS file that requires debugging.
The Buffer class in Node.js is designed for handling raw binary data. Each buffer manages some memory that is allocated outside of V8. Buffers have some similarities to arrays of integers but cannot be resized and have a variety of methods that are meant specifically for working with binary data.
The WASI class implements the WASI system, providing convenient methods for interacting with WASI-based apps. Every WASI instance represents a unique sandbox environment. For security reasons, WASI instances must specify their command-line parameters, environment variables, and sandbox directory structure.
When running an application, Callbacks are started by events. Node.js will continue to execute the code without waiting for the output. Once all of the code has been executed, the outputs are collected and the callback function is executed. This operates in a continuous loop, hence the name event loop.
The Reactor Pattern prevents Input/Output operations from being blocked. It provides us with a handler that is associated with I/O operations. When I/O requests are generated, they are routed to a demultiplexer, which manages concurrency and collects the requests as events.
There are two ways in which I/O operations can be performed:
1. Blocking I/O: The application makes a function call and then pauses execution at a specific point.
2. Non-Blocking I/O: The application will make a function call and then continue execution without waiting for the results. It is known as 'Asynchronous'.
The URL module contains utilities for resolving and parsing URLs. The getters and setters implement the properties of URL objects on the class prototype, and the URL class is available on the global object.
The new URL() method is an inbuilt application programming interface of the URL module which creates a new URL object by parsing the input relative to the base. If the base is passed as a string, it will be parsed equivalent to the new URL(base).
Syntax : new URL(input[, base])
V8 JavaScript engine was created to improve the performance of JavaScript execution in Google Chrome and Chromium web browsers, which is open-source and written in C++. V8 is the popular runtime for Node.js. V8 was initially intended to improve the speed of JavaScript execution within web browsers by converting JavaScript code into more efficient machine code. V8 uses a JIT (Just-In-Time) compiler to turn JavaScript code into machine code during execution.
The best way to prepare for an interview is to create a mock interview environment. Answering the same questions out loud to someone or in front of a webcam helps you prepare for possible interactions with your interviewer. Also, they can help ease some of the nervousness that often comes with interviews.
The Node team has an excellent process for conducting code challenges, so it makes sense to ask them about their process for interviewing.
