25 Most Asked Node JS Interview Questions

It is used to collect information about specific events and form quests, thereby providing the so-called Event Que. This is another interview question on Node JS that is not directly related to any Node feature. However, it is still important to know what Node JS Express is, as it is explicitly designed for Node JS. Get your enrollment process started by registering for a Pre-enrollment Webinar with one of our Founders.

The Node JS Processing paradigm is heavily influenced by the JavaScript Event-based model and the JavaScript callback system. As a result, Node.js can easily manage more concurrent client requests. The event loop is the processing model’s beating heart in Node.js. A single thread from the Thread Pool is assigned to a single complex request. This thread is responsible for completing a particular blocking request by accessing external resources, such as computation, database, file system, etc. Being single-threaded but scalable, Node.js allows developers to take advantage of multiple processes.

However, during the Node.js coding task, specialists should submit sample projects. Candidates should describe their vision of the entire process, beginning with identifying the problem and delivering code to production. Team workflow is a necessary process to define because it lets one understand how to communicate with a remote team, solve conflicts, integrate different time zones, etc. It may not be compulsory in the list of Node.js interview questions since many senior developers write JavaScript code. In general, an understanding of a team workflow is expected from seniors.

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As the hiring manager, you can give several coding challenges to a junior developer candidate. A callback function is invoked upon the completion of a job. It permits other codes to continue in the meanwhile and avoids blocking. Node.js is an asynchronous platform that mainly relies on callbacks. A single complex request is assigned a single thread from the Thread Pool. This thread is in charge of performing a specific blocked request by accessing external resources such as computers, databases, file systems, etc.

junior node js developer interview questions

The reactor pattern is yet another pattern for nonblocking I/O operations. However, this is commonly utilized in any event-driven design. In general, a buffer is a temporary memory mainly utilized by streams to store data until it is used. Pads, which are presented with more use cases than JavaScript’s Unit8Array, primarily represent a fixed-length series of bytes.

Junior Developer Roles and Responsibilities

Mongoose – Mongoose is also a Node.js web application framework that makes it easy to connect an application to a database. It is a JavaScript library based on WebSockets and other technologies. Unlike WebSockets, Socket.IO allows you to send messages to all connected clients. It isn’t easy to use proxying and load balancers in WebSockets. Socket.IO supports gradual degradation and automatic reconnection when the connection is broken and is easier to use. It may seem like Socket.IO is the best tool for live communication.

  • First, though, it’s important to understand a junior developer’s roles, responsibilities, and requirements so that you can ask targeted questions during the interview.
  • The requests are then routed through the Event Loop one by one.
  • In interview questions on Node.js, it is also essential to pay attention to how they interact with the team, their values, and their work attitude.
  • Node.js indeed spawns child threads for some tasks like asynchronous I/O.
  • API is something both front-end and back-end developers have to work with.
  • Real estate software development company handles complex challenges by creating products and software for a very demanding domain.
  • Async processing on a single thread under usual web loads allows us to achieve more performance and scalability than the general thread-based implementation.

It is important to know that an automatic flow is created in the event loop. There is only one thread, which is an event loop in Node.js that determines which thread will execute callback functions at any given time. Coding challenges are a popular way to assess junior developers since they can directly test their coding skills. Hiring managers use coding challenges to determine whether candidates can write clean, efficient, and error-free code. Challenges may also involve developing the correct algorithm to solve an issue or testing more on object-oriented concepts and designing a system.

This prevents any blocking and enables other code to run in the meantime. An event-driven programming approach uses events to trigger various functions. An event can be anything, such as typing a key or clicking a mouse button. A call-back function is already registered with the element executes whenever an event is triggered.

What Is The Difference Between Mobile And Web Development?

ExpressJS – Express is a flexible Node.js web application framework that provides a wide set of features to develop web and mobile applications. It is a NoSQL, cross-platform, document-oriented database that provides high performance, high availability, and easy scalability. Stubs are functions that replicate the functionality of specific modules. They are frequently used in tests since they can answer problems that may arise in the modules. 12 tips on how to develop a cryptocurrency trading app In this article, we share our knowledge and experience in developing cryptocurrency trading applications. Development of high-load fintech applications Do your system still work on heavy load?

Composition determines a class as the sum of its parts, whereas inheritance separates one class from another. Through inheritance, classes and objects are closely linked. If to change the parent or superclass, you can break your code. Classes and objects are loosely coupled in composition, and it’s easier to change component parts without breaking the code. Because of flexibility, many developers consider composition a better technique. The Multi-Threaded Request/Response Stateless Model is not followed by the Node JS Platform, and it adheres to the Single-Threaded Event Loop Model.

HTML Mistakes Web Developers Should Avoid

A lot of frameworks use blocking IO, they use pool of threads to perform concurrent operations. The main disadvantage of this approach is thread overhead. Each thread requires ≥ 1MB of memory, it means that number of threads are limited by server.

junior node js developer interview questions

It also supports legacy encodings such as ASCII, utf-8, etc. Outside of the v8, it is a fixed (non-resizable) allocated RAM. Duplex streams can be read and written in both directions (for example, net.Socket). When the task is completed, the response is passed to the Event Loop, returning the answer to the client. The Event Loop handles simple requests like I/O Polling and returns the results to the appropriate customers. Overall, Node.JS is one of the best tools for JavaScript-based server-side development.

Read about top 10 Functional Testing Tips in Symfony Written by Oksana T. Node.JS is truly one of the most useful web development tools of late. It is based on JavaScript and allows you to be flexible and easily adaptable to most web development scenarios. With keyword await it is simply the difference between the time that was before and after execution . In the second case, we need to call then() function to find the difference between these two values .

What are the core modules of Node.js?

The question indirectly touches on some other technologies, such as C# and Java, for example. Besides, it covers some obsolete types of Node.js usage, such as relational databases. It is about responsiveness under intensive CPU computation. Although the question may seem strange, it is important to check whether the candidate knows what he is working with.

Overall, Node JS is just one of the best tools on the market when it comes to server-side development based on JavaScript. Node JS is a JavaScript-based tool designed to perform internal development and implementation processes. If you are the one to hire, you are 36 questions away from finding your perfect candidate. A broken access control attack is a security threat when an attacker gets unauthorized access to some parts of the website. An index contains a field value and a pointer to a specific record. Indexing speeds up the search in the database because it tells the app which field to look up, and the SQL engine doesn’t have to look through each and every row.

Security is the number one concern of modern-day Internet users. It’s not optional but obligatory to keep your app safe and invincible. This is why you have to ensure your developers know what security threats to expect and how to prevent them. The event-based model of Node.js solves the problem of blocking input-output operations and uses event loops instead of threads. The technical example of the bind() function written using apply() is one of those Node js exercises depending on the candidate’s experience and understanding. The solution may differ, but it’s important the candidate can provide one.

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The questions for 1-year experienced Node.js developers are more theoretical than practical. However, novice specialists should be well aware of the basics. They should understand technical but straightforward coding junior node js developer concepts such as event loops and event programming during interview questions on Node.js. During the technical interview, they should clarify how coding works with Node.js and its advantage over other technologies.

The point of this question is to see if they have experience working with it. Child_process is a module enabling accessing the functionalities of the OS by running any system command inside a child process. Asynchronicity means that the following operation doesn’t wait for the previous one to be completed. The asynchronicity in Node.js works due to its event-based, non-blocking I/O model. Relational databases, such as PostgreSQL and MySQL, store data in tables. Non-relational databases, such as MongoDB, store data in JSON documents.

Explain asynchronous and non-blocking APIs in Node.js.

The WASI class implements the WASI system called API and extra convenience methods for interacting with WASI-based applications. Every WASI instance represents a unique sandbox environment. Each WASI instance must specify its command-line parameters, environment variables, and sandbox directory structure for security reasons. The V8 engine, developed by Google, is open-source and written in C++. V8, unlike the other engines, is also utilized for the popular Node.js runtime.

It is, without a doubt, the most fundamental question about Node.JS. Naturally, this is frequently the first or one of the first questions asked in an interview. Node.JS developers in the interview can be more essential https://xcritical.com/ than the advanced ones – in the end, they define the path of the rest of the interview. 10 Functional Testing Tips in Symfony Functional tests verify the integration of different levels of the application .

JavaScript Basics

In the original client/server model, the web client is always the initiator of transactions — it’s the one to request data from the server. The server can’t independently send data to the client until it receives a request. The long polling technique was introduced to solve this problem. As for the question “To which level should you normalize your database so that it is acceptable? Yet, the candidate’s answer can show you how confident they feel about databases and how meticulous they are. But if know the answers to all questions in this article, you will definitely make a good impression on your interviewer.

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