Node.js interview questions are essential for preparing for a software developer interview. Node.js is used by top companies such as Netflix, LinkedIn, NASA, Trello, PayPal, Walmart, Uber, Twitter, Yahoo, eBay, and GoDaddy because programming in the Node.js environment is faster, easier, and reduces development time and overall time-to-market.
The demand for Node.js programmers is increasing at an alarming rate. The Node.js interview questions listed below will familiarize you with the types of questions you may face during your interview. In this article, we covered both basic and advanced Node.js interview questions. If you practice these Node.js interview questions, you will undoubtedly ace your next software developer interview.
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This article will look at the Node.js interview questions that you may expect during software developer interviews.
Here’s what we’ll cover:
Some employers may use a combination of these basic Node.js interview questions depending on the job type. So, ensure that you know the important topics ahead of time.
This is one of the most frequently asked Node.js interview questions. Node.js is a popular web application framework popular for server-side scripting to build scalable programs. It is built on Google Chrome’s V8 JavaScript Engine. Nide.js comes under MIT license and is free to use. It extends JavaScript API to offer usual server-side functionalities. It is generally for the following purposes:
You must consider the following factors while answering such Node.js interview questions:
Node.js employs a single-threaded model that supports async processing. Async processing enables the application to perform better and makes it more scalable under web loads. Thus, Node.js has a single-threaded model with event looping.
In Node.js, an event loop is responsible for all the asynchronous callbacks in an application. It is an endless loop that awaits tasks, executes them, and sleeps till it receives the next tasks.
It executes tasks from the event queue only when there is no ongoing task, i.e., the call stack is empty. It is the event loop that allows Node.js to have non-blocking I/O. You must know that the event loop allows you to use callbacks and promises.
A function that is called after a given task is a callback function. It allows other code to run meanwhile and prevents any blocking. Node.js heavily relies on callback as it is an asynchronous platform. All Node APIs are written to support callbacks.
A problematic phenomenon for a JavaScript developer when he tries to execute multiple asynchronous operations consecutively is termed callback hell. An asynchronous function is one that requires some external activity completion before processing a result. These asynchronous functions require a callback function to tackle errors and process the result.
A promise in Node.js is a placeholder for a value that will be available in the future. Promises in Node.js allow asynchronous methods to return values like synchronous methods wherein the asynchronous method returns a promise for the value in the future instead of the final value. They have separate callbacks that would be executed for success/ failure and handling timeouts. Promises fall in the following three different states:
You must answer such Node.js interview questions with a relevant yet precise reason explaining why you would choose one over the other. The reasons for selecting promises over callbacks are as follows:
The API functions in Node.js are of two types, namely:
Blocking functions execute synchronously. Every other code is blocked from running until an awaiting I/O event occurs.
Non-blocking functions execute asynchronously, i.e., multiple I/O calls can be performed without the program’s execution being halted.
REPL is the abbreviation for Reading Eval Print Loop. It represents a computer environment similar to a Windows console or Unix/Linux shell wherein a command is entered, and the system reverts with an output. It’s an easy-to-use command-line tool for processing Node.js expressions.
You can also elaborate on REPL while answering this Node.js interview question.
These were the most commonly asked Node.js interview questions. Scroll through the following section for some advanced Node.js interview questions for your tech interview prep.
Here are a few advanced Node.js interview questions and answers for senior positions. If you’re interviewing for a position as a senior software developer, practice these questions to ace the interview.
A buffer class holds raw data just like an array of integers but corresponds to a raw memory allocation outside the V8 heap. These aren’t resizable and have several methods specifically for binary data. Pure JavaScript is not compatible with binary data, so a buffer class comes into play.
This is one of the most common Node.js interview questions to gauge your knowledge of vital topics in Node.js. Piping in Node.js is the mechanism that connects the output of one stream to another, i.e., it connects multiple streams. It retrieves data from one stream and passes the output to another stream.
Node.js streams are instances of EventEmitter. You can use them to work with streaming data in Node.js, especially for handling and manipulating streaming large files (such as videos and mp3) over the network. Streams use buffers for temporary storage. There are four main types of streams.
Modules in Node.js applications are similar to JavaScript libraries. They include a set of functions. You have to use the require() function (the parentheses contain the module’s name) to add a module in a Node.js application. The following modules provide the basic functionality to a web application:
A middleware function has access to the response object, request object, and the next middleware function in the application’s request-response cycle. A variable named next denotes the next middleware function. Middleware finds usage in between your request and business logic. You can also write your own middleware for a specific use case. The primary tasks that the middleware functions perform are:
A reactor pattern is a pattern for non-blocking I/O operations generally used in any event-driven architecture. It has two components:
This is one of the most crucial Node.js interview questions that an interviewer asks to gauge your understanding of the system design and preferences. Google’s v8 is the most evolved and fastest JavaScript and Web assembly engine. It is open-source and thus has a huge community helping develop features and bug-fixing. The V8 engine is portable to almost every machine.
Exit codes of Node.js provide an idea of the reason behind code termination. Some exit codes are as follows:
Node.js applications do not use multiple core systems. Instead, they run on a single processor. In Node.js, the cluster mode helps startup multiple node.js processes, thus having multiple instances of the event loop.
When you use a cluster in a Node.js app behind the scenes, there are numerous node.js processes created, but there is also a parent process called the cluster manager. A cluster manager monitors the health of the individual instances of the application.
WASI stands for the WebAssembly System Interface. It is a capability-oriented set of APIs built to standardize the sandboxed execution of WebAssembly modules outside of browsers.
WASI was introduced with the idea in mind that it is possible to use the underlying operating system via a collection of POSIX-like functions and further enable the application to use resources more efficiently and features requiring system-level access.
You must practice the following Node.js coding interview questions to gear up for your next tech interview.
Here are some sample Node.js technical interview questions for you to practice. Preparing answers to these questions can help you ace your tech interview.
This completes our list of important Node.js interview questions for interview preparation. You must check out domain-specific preparation strategies and questions on the interview questions page.
Q1. Does Netflix include Node.
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The 11 Neural “Power Patterns” For Solving Any FAANG Interview Problem 12.5X Faster Than 99.8% OF Applicants
The 2 “Magic Questions” That Reveal Whether You’re Good Enough To Receive A Lucrative Big Tech Offer
The “Instant Income Multiplier” That 2-3X’s Your Current Tech Salary
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