Do you wish to crack the job into the most renowned role – "NodeJs Developer?" Are you willing to work with the new business module or want to work in a big tech development company? Curious about creating new applications or technology with the NodeJs Developer tag? To help you crake the interview irrespective of level, such as beginner or professional, these are the question you can rely on. Since we know the most crucial step for someone looking for work is the job interview. We make you well-prepared for a NodeJs interview.

  • Node.js is a server-side technology that is extremely popular and is being used by more and more businesses. It’s always a good idea to get ready and brush up on your interview techniques in advance if you’re getting ready for a career shift and have an upcoming job interview. Although a few Node.js interview questions are frequently asked across all interview types, we advise that you focus on questions that are unique to your business as you prepare. We have created a thorough list of frequently asked Node.js interview questions and the most effective responses to each one. This will also aid in your comprehension of the core ideas of NodeJS.

Frequently Asked Questions (FAQs)

1.Is NodeJS good for MVPs and Prototyping?

A large repository of modules included with Node.js called npm allows developers to experiment and create MVPs rather quickly. The efficiency and scalability of Node are an advantage in case the app needs to be scaled up or expanded in the future.

However, relying on npm third-party modules has some drawbacks (such as the inability to assess module quality or the many modules to choose from). Finding developers with Node.js development experience is crucial for this reason.

2. What is Blocking IO?

I/O stands for input and output. Anything from reading and writing to local files to sending an HTTP request to an API is possible. Blocking IO simply implies that if a server receives another IO request while processing an IO request for a client, the new request (and all subsequent requests) will be blocked until the previous request is finished. This is incredibly wasteful and calls for multi-threading to handle several requests at once.

3. How to install a package using NPM?

Using NPM, we must execute the command to install a package.

npm install <package-name>[flags]

4. What is the name of the file that NPM utilizes to keep track of every dependency that has been installed for a project?

Package.json is the name of the file that NPM uses.

5. Can Node.js be used to create desktop applications?

In essence, Node.js allows you to create desktop and mobile applications. The JavaScript runtime environment, not Node’s personality as it is a normal server tool, is the reason the answer is positive. You can take portions of the code from a Web app and use frameworks like Electron to create a desktop version of the program. With this method, developers may construct native desktop applications without having a thorough understanding of Objective-C or C# by using only JavaScript, HTML, and CSS.

6. What is a debugger in NodeJS?

The debugger debugging tool is part of Node.js. Start NodeJS with the debug parameter and the path to the script you want to debug to activate it.

A breakpoint at that location in the script’s source code can be activated by inserting the statement debugger; there.

7. Can NodeJS be used to build Machine Learning and AI Algorithms?

Node.js provides libraries and tools for integrating AI-based components into apps; TensorFlow.js for machine learning is one such example; nevertheless, this isn’t really the best application for this technology. For AI and machine learning scripting, Python and Ruby would be much better options.

8. Explain error-first callback.

Data and errors can both be passed through error-first callbacks. The error must be passed as the first parameter, and it must be examined to see what went wrong. To pass data, further parameters are necessary.

9. Enlist the features of NodeJS.

Node JS uses Java as its programming language and is extremely scalable because it runs in a single thread. Additionally, it uses asynchronous, event-driven I/O. Instead of numerous and various threads, this allows access to a single thread. It’s possible to attain good performance even with just one thread.

10. How is NodeJS scalable?

The Node JS application has both horizontal and vertical scaling options. Additionally, it suggests that you must distribute the traffic among many CPU threads and run multiple instances of your software on a single machine. Additionally, Node.JS has a cluster module, which is incredibly useful. When it comes to horizontal scaling, it functions much like any other standard backend application.

NodeJs Interview Questions for Freshers

1. What is NodeJS? What are the key areas where NodeJS is applicable?

An open-source, cross-platform runtime environment and library for JavaScript are called Node.js, and it is used to run web applications outside of the client’s browser. For building server-side web applications, it is employed.

Node.js’s asynchronous, the event-driven architecture makes it ideal for data-intensive applications. You can use web apps with a lot of I/O, such as video streaming websites. It can also be used to create distributed systems, network applications, general-purpose applications, and real-time web applications.

2. What is the importance of NodeJS?

Building scalable network apps is simple with Node.js. It has several benefits, including:

      1. It is fast

      1. It seldom blocks

      1. There is a single programming language and data type available.

      1. The world is asynchronous.

      1. It produces high concurrency.

    3. State the working of NodeJS.

    To communicate with the web application, clients make requests to the web server. Demands may be blocking or non-blocking:

      1. Requesting data
      2. Data updating and deletion
      3. The incoming requests are retrieved by Node.js and added to the Event Queue.
      4. Following that, each request is routed individually through the Event Loop. It determines whether the requests are straightforward enough not to need any outside assistance.
      5. Simple requests (non-blocking activities), like I/O Polling, are processed by the Event Loop, which then sends the results to the respective clients.

      A single complex request receives a single thread from the Thread Pool. By using external resources like computing, a database, a file system, etc., this thread oversees performing a specific blocked request.

      4. Why is Node.js Single-threaded?

      Async processing is single-threaded in Node.js. Instead of the conventional thread-based design, better performance and scalability can be obtained by performing async processing on a single thread under typical web loads.

      5. How does NodeJS handle concurrency if it is single-threaded?

      The Node JS Platform adheres to the Single-Threaded Event Loop Model rather than the Multi-Threaded Request/Response Stateless Model. The JavaScript event-based model and callback mechanism have a significant impact on the Node JS Processing paradigm. Node.js can easily handle more concurrent client requests as a result. The beating core of the Node.js processing model is the event loop.

      6. How are packages managed in a node.js project?

      Numerous package installers and their corresponding configuration files can control it. Use npm or yarn the most often among them. Both offer enhanced features for controlling environment-specific configurations for practically all javascript libraries. We utilize package.json and package-lock.json to manage the versions of the libraries that are installed in a project so that moving the app to another environment is simple.

      • 7. How is Node.js superior to other widely used frameworks?
        • Contrary to other frameworks where developers must employ thread management, Node.js offers ease in development thanks to its non-blocking I/O and even-based approach, which results in quick response times and concurrent processing.
        • It is powered by the very effective Chrome V8 engine, which was created in C++ and continues to get better.
        • Additionally, since Javascript will be used in both the front end and the back end, the development will go much more quickly.
        • Finally, there are plenty of libraries, so we won’t have to keep inventing things.

        8. How does “Control Flow” manage the function calls? What are the steps?

        • Control the execution’s timing
        • Gather data and restrict concurrency
        • Call the program’s subsequent step.

        9. What benefits come from utilizing promises rather than callbacks?

        The primary benefit of using promises is that you receive an object to determine what needs to be done after the async job is finished. As a result, callback hell is avoided, and the code is more manageable.

        10. How does Node.js deal with the issue of I/O operations blocking?

        Since the Node contains an event loop, all I/O actions can be handled asynchronously without interfering with the main function.

        So, for instance, the event loop will be used to schedule network calls rather than the main thread (single thread). Additionally, if there are several of these I/O calls, each will be queued appropriately and executed independently (other than the main thread).

        So, even though JS is single-threaded, I/O operations are performed without blocking.

        11. What is NPM?

        The Node Package Manager, or NPM, oversees overseeing all the Node.js packages and modules.

        Two primary features of Node Package Manager are:

        Provides node.js packages and modules in online repositories that may be searched at

        Installs Node.js packages using a command-line tool and manages Node.js versions and dependencies.

        12. Why is Node.js favored over Java and PHP as backend technologies?

        Node.js is favored for several reasons, including:

        • Node.js is quick.
        • The developer gets access to more than 50,000 packages with Node Package Manager.
        • Node.js is ideal for real-time, data-intensive web applications since it never waits for an API to return data.
        • Because the server and client share the same code base, there is better code synchronization.
        • Since Node.js is a JavaScript library, using it in projects is simple for web developers.

        13. What are node.js buffers?

        In general, a stream uses buffers as temporary memory to store data until it is needed. In contrast to JavaScript’s Unit8Array, buffers are introduced with more use cases and are mostly intended to represent a fixed-length sequence of bytes. Legacy encodings like ASCII, utf-8, and others are supported as well. Outside of the v8, it is a fixed (non-resizable) allocated memory.

        14. What is JSON?

        JavaScript Object Notation, or JSON. It has mostly supplanted XML and is an incredibly popular data interchange standard. Any text editor may be used to read and write it because it is so standard and straightforward. Here is an illustration of a basic JSON object.

        It is only a collection of key-value pairs, as you can see. It can even store layered data and represent more complicated datasets.

        A crucial goal for Node.js programmers, interoperability at scale, has been made possible for JavaScript developers through JSON.

        15. What is non-blocking IO?

        Non-blocking, asynchronous architecture is the foundation of Node. This implies that any activity requiring a lengthy amount of time to complete, such as file access, network communication, and database operations, is requested and delayed until the outcomes are ready and returned via a callback function.

        You can start a data request for another user using a non-blocking request without having to wait for the outcome of the request for earlier users. You can start both requests simultaneously.

        Since the server may process numerous requests simultaneously, non-blocking I/O reduces the requirement for multi-threading.

        NodeJs Interview questions for Experienced Professionals

        1. What is an Event loop in NodeJS?

        i. The event loop, which is at the core of Javascript and Node.js, oversees the planning of asynchronous tasks. Despite JavaScript’s single-threaded nature, the event loop enables Node.js to conduct non-blocking I/O operations by offloading tasks to the system kernel wherever available. To fully comprehend the event loop, you must first comprehend the many stages that make up the event loop as well as what takes place during each step.
        ii. Timers – This is where the operations that were planned using setTimeout() or setInterval() will be carried out.
        iii. IO Callbacks – The majority of callbacks will be handled here. This is the userland code since all Node.js userland functionality is essentially contained in callbacks (for example, a callback to an incoming HTTP request initiates a series of callbacks).
        iv. IO Polling – Checks for new events that will be handled on the following run.

        v. Set Immediate- Runs all callbacks registered with set Immediate when set to “immediate” ().
        vi. Close- All on(‘close’) event callbacks are handled here.
        vii. The event loop is a set of previously mentioned phases with duties that are carried out in a round-robin fashion. JavaScript code can only be executed by a single thread, which also happens to be the thread that is currently executing the event loop. The event loop performs call-back execution.
        viii. The event loop will adjust to this situation and block for a while in the polling phase to wait for fresh external events to arrive if the application is idle, which means that there are no pending tasks (Timers, callbacks, etc.).

        2. What are promises in NodeJS?

        In our JavaScript code, a promise can be formed (and therefore in NodeJS). Alternatively, it can be returned from a package for an external node.
        A function should be called on a promise by the code that uses it. It accepts two parameters that are anonymous functions. If the promise is fulfilled, the first function runs, and if the promise is not, the second function runs.

        3. What are LTS releases in NodeJS?

        Long-Term Support, or LTS, is a designation given to release lines that the Node.js project will continue to support and develop. LTS comes in two flavors:
        Active, which is continuously improved and maintained, and Maintenance line, which is maintained just briefly.

        4. Difference between Spawn() and Fork().



        As soon as the child process begins operating, this begins sending data from the child process back to the parent process.

        While we can use a global module name process to send data from the child process and in the parent module using the name of the child the process to send to the child process, this does not automatically transfer data.

        Using a command, establishes a new process rather than continuing to operate on the same node process.

        Although it creates a number of distinct processes (child processes), they all share the same node process as the parent.

        No new V8 instance is created in this.

        A new instance of V8 is created in this.

        When we want the child process to give the parent process a lot of data, we use it.

        It is used to keep the main event loop and computationally demanding activities apart.

        5. What function does the ExpressJS package in NodeJS serve?

        On top of Node.js, the ExpressJS package or framework is created to hasten the creation of single-page, multi-page, and hybrid server-based applications. The backend component of the MEAN stack, according to some, is Express.

        6. Difference between NodeJS and Ajax.

        Client-side technology called Ajax allows for content updates on web pages without requiring a page refresh. Server-side JavaScript called Node.js is used to create server software. Furthermore, although Ajax only retrieves data or executes scripts, Node.js is a full-featured programming environment.

        7. What are the security mechanisms in NodeJS?

        Authorization Codes: Node.js is protected from unauthorized third parties using authorization codes. Anyone attempting to reach Node.js uses the network of the resource provider’s GET request.
        Certified Modules: The Node.js libraries are scanned by certification modules, which act as filters, to see if any third-party code is present or not. Certifications can be used to find any hacking.
        Curated Screening Register: All the packages (code and software) are examined as part of a quality control procedure to guarantee their security. This scan aids in preventing unauthorized or shaky libraries from entering your application.
        Regular Updates: The most recent Node.js version should be downloaded to avoid hackers and attacks.

        8. How does assert in NodeJS work?

        In Node.js, tests are written using Assert. Only when one of the active test cases fails is feedback given. The module provides you with a set of assertion tests to test invariants. Although Node.js uses it internally, if you use the required (‘assert’) code, you can also use it in other applications.

        9. Explain readFile and createReadStream in Node.js.

        There are two methods offered by Node.js for reading and executing files: readFile and createReadStream.
        The readFile process is fully buffered and only responds if the entire file can be read after being loaded into the buffer. This process uses a lot of memory and gets sluggish if the file size is big.
        The createReadStream process treats the entire process as a sequence of events and is only partially buffered. The entire files are divided up in this procedure, and each chunk is analyzed separately before being transmitted as a response one at a time. CreateReadStream works well for reading and processing huge files, unlike readFile.

        10. Does NodeJS provide a Debugger?

        Node.js offers the debugging client and a built-in TCP protocol. Use the following argument before the name of the JS file you want to debug if you want to debug it.

        11. What is middleware in NodeJS?

        A middleware, like your route handlers, is essentially a function that will accept the Request and Response objects. Once your middleware code is finished, you should call another function that you have as a third argument. This implies that you can delay moving on to the next action until asynchronous database or network activities are complete.
        In the request-response cycle of an application, middleware functions are functions that have access to the request object (req), the response object (res), and the subsequent middleware function. A variable with the name next is frequently used to identify the next middleware function.

        12. What is the importance of BufferClass in NodeJS?

        Since the buffer class is a global class, applications can access it without importing the buffer module. A raw memory allocation outside of the V8 heap, a buffer is a type of array of numbers. Buffers cannot be shrunk or grown.

        13. Explain EventEmitter in NodeJS.

        Node.js’s events module enables us to design and manage unique events. The “EventEmitter” class included in the Event module can be used to create and manage unique events.

        14. What is SocketIO?

        A bi-directional, real-time, event-based communication library is called SocketIO. It is made up of a client-side library and a NodeJS server package. It is constructed over EngineIO. It consolidates numerous transports, such as WebSockets and AJAX long-polling, into a single API. Data transmission and reception are made possible for developers without concern for cross-browser compatibility.

        Due to SocketIO’s ability to make WebSockets both usable and dependable, NodeJS has become increasingly popular. Version 1.0 is a significant step forward in its development, and the removal of EngineIO has created some intriguing opportunities for the NodeJS ecosystem.

        15. What is WASI in NodeJS?

        Web assembly uses the WASI API in node.js, which is implemented using the WASI class, to provide an implementation of the WebAssembly System Interface specification. The introduction of WASI was done with the knowledge that a set of POSIX-like functions might be used to access the underlying operating system, allowing the application to utilize resources more effectively and make use of features that call for system-level access.


        A prominent server-side technology among Mean stack developers is NodeJS. Developers of Node.js are awarded lucrative salaries. You will be able to pass the interview with complete confidence if you use the node js interview questions provided here. The most important and fundamental inquiries about NodeJS are answered in this FAQ. All of these will be very helpful to you in your Node js interview and if you’re prepared to devote yourself to longer-term education.


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