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Node.js is a powerful JavaScript-based platform for developing online chat applications, video streaming sites, single-page applications, and many other I/O intensive web applications. It is built on Google Chrome's JavaScript V8 Engine and used by large established companies and startups (Netflix, Paypal, NASA, and Walmart, to name a few).
Node.js is open-source and free and used by thousands of developers worldwide. It brings many benefits, making it a better choice than other server-side platforms like Java or PHP.
In this blog, we will see some of the top Node.js interview questions. This blog also includes Node.js interview questions for experienced candidates.
1. What is Node.js?
Node.js is an impressive framework built on Chrome V8 JavaScript that compiles JavaScript directly into native machine code. It is a lightweight framework for building server-side web applications and extends the JavaScript API to offer standard server-side functionality. It is usually used for large-scale application development, primarily for video streaming sites, single-page applications, and other web applications.
2. What is the purpose of Node.js?
These are the following purposes of Node.js:
" Real-time web applications
" Network applications
" Distributed systems
" Universal application
3. What are the advantages of Node.js?
Below are the main advantages of Node.js:
" Node.js is asynchronous and event-driven. All Node.js APIs are non-blocking, and their server does not wait for the API to return data. Once called, it moves to the following API, and the Node.js event notification mechanism from the previous API call responds to the server.
" Node.js is very fast because it is based on Google Chrome's V8 JavaScript engine. Its library is very quick in code execution.
" Node.js is single-threaded but highly scalable.
" Node.js provides no-buffering functionality. Its app never stores any data. Outputs data in blocks.
4. Explain the architecture of a Node.js web application.
The web application is divided into 4 layers:
Client Layer: The client layer includes web browsers, mobile browsers, or applications that can send an HTTP request to a web server.
Server Layer: The server layer includes the web server that can intercept the client's request and forward the response to them.
Business layer: The business layer contains the application server used by the web server to perform the required processing. This layer inter with the data layer through the database or external programs.
Data Tier: The data tier contains databases or any data source.
5. What are the LTS releases of Node.js?
LTS version of Node.js acquires all essential bug fixes, security updates, and performance progress. These versions are sustained for at least 18 months and concentrate mainly on stability and security. Modifications made in LTS releases are limited to bug fixes, security upgrades, npm, documentation updates, performance improvements, etc.
6. List the main security implementations within Node.js.
The main security implementations in Node.js are:
" Authentication
" Dealing with an error
7. What is the purpose of the module?
In Node.js, a module summarize all related code into a single unit of code that can be analyzed by moving all relevant functionality into a single file. You can export a module with a module and export a process that allows you to import it into another file with the necessary keyword.
8. Why is Node.js favored over other backend technologies like Java and PHP?
Some of the causes why Node.js is favored include:
" Node.js is very quick
" Node Package Manager has more than 50,000 packages obtainable for developers.
" Ideal for data-intensive, real-time web applications because Node.js never pauses for an API to return data
" Better integration of code between server and client thanks to the same code base
" It's easy for web developers to use Node.js in their projects because it's a JavaScript library.
9. What is meant by event-driven programming?
Event-driven programming uses events to trigger various functions. An event can be a keystroke or a mouse click. A callback role is registered with the element and will be fired whenever an event is fired.
10. What is an event loop in Node.js?
Event loops operate asynchronous callbacks in Node.js. It is the foundation of non-blocking I/O in Node.js, making it one of the most important environmental features.
11. Distinguish between process.nextTick() and setImmediate()?
Difference between method and product. This is achieved by using nextTick() and setImmediate(). next Tick() defers the execution of action until the next iteration of the event loop or simply calls a callback function once the current execution of the event loop is complete. At the same time, setImmediate() executes a callback on the next iteration of the event loop and returns authority to the event loop for any I /O operations.
12. How does "Control Flow" manage function calls?
The control flow does the following work:
" Check the order of execution
" Collect data
" Limit concurrency
" Call the next step in the program
13. What is a fork in node JS?
A fork is generally used to create child operations. In node, it is utilized to create a new instance of the v8 engine to run code for multiple workers.
14. Why is Node.js single-threaded?
Node.js was created expressly as an experiment in asynchronous processing. It was to test the new theory of doing asynchronous processing on a single thread over the existing implementation of thread-based scaling through different frameworks.
15. Explain the tasks of the terms used in the Node REPL.
Below are the terms used in the REPL with their defined tasks:
Read: Reads user input, parses the information into a JavaScript data structure, and stores it in memory.
Eval: Takes and evaluates a data structure.
Print: Used to print the result.
Loop: Repeats the above command until the user presses ctrl-c twice to exit.
16. Is it possible to evaluate simple expressions using Node REPL?
Yes. You can evaluate simple expressions using the Node REPL.
17. Is it possible to access the DOM in Node?
No, it is not possible to access the DOM in Node.
18. What is a REPL in Node.js?
REPL stands for reading Eval Print Loop. Specifies a computer environment, such as a windows console or Unix/Linux shell, where you can type a command, and the computer responds with output. It is convenient when writing and debugging codes. The REPL includes Node.js.
19. Improving Node.js performance through clustering.
Node.js applications execute on a single processor, which means they don't use a multi-core system by default. Cluster mode is used to run multiple node.js processes, thus having various event loop instances. When we start using clusters behind the scenes of a nodejs application, numerous node.js processes are created. There is also still a parent process called the cluster manager responsible for monitoring the health of individual instances of our application.
Clustering in Node.js
20. What is a thread pool, and which library works with it in Node.js
The thread pool is maintained by the libuv library. libuv is a cross-platform C library that supports asynchronous I/O operations such as file systems, networks, and concurrency.
Thread pool
21. What is WASI, and why is it being implemented?
WebAssembly provides an implementation of the WebAssembly System Interface specification through the WASI API in node.js implemented using the WASI class. The introduction of WASI was done with an eye toward its possible use by the underlying operating system through a collection of POSIX-like features, which further allowed the application to utilize resources more efficiently and features needing system-level access.
22. How do worker threads differ from clusters?
Cluster:
" On each CPU with IPC, there is one process that communicates.
" Groups can be helpful if we want multiple servers to accept HTTP requests over a single port.
" Processes are created in each CPU and, therefore, will have a separate instance of memory and node, leading to memory issues.
Working Threads:
" There is only one multi-threaded process in total.
" Each thread has one instance of Node (one event loop, one JS module) with most APIs available.
" Shares memory with other threads (e.g., SharedArrayBuffer)
" This can be used for CPU-intensive data processing or file system access. Because NodeJS is single-threaded, synchronous tasks can be more efficient using worker threads.
23. What is an event emitter in Node.js?
EventEmitter is a Node.js class that includes all objects that are basically capable of emitting events. This can be done by tying up the named possibilities emitted by the object using the event emitter.on() function. So whenever this object calls even, the attached functions are called synchronously.
24. Explain the concept of snippets in Node.js?
Stubs are used when writing tests, which are essential to development. It replaces the entire function being tested.
This operates in scenarios where we need to test:
" External calls that delay tests and are challenging to write (e.g., HTTP calls / DB calls)
" Activating different outcomes for a piece of code (e.g., what happens when an error is raised/if it passes)
25. What is the function of control flow?
A control flow function is a code that runs between multiple asynchronous function calls.
26. What is the buffer class in Node.js?
The buffer class stores raw data similar to an array of integers but corresponds to a raw memory allocation outside the V8 heap. The buffer class is used because pure JavaScript is incompatible with binary data.
27. What is a pipeline in Node.js?
Piping is a mechanism that connects the output of one stream to another. It is usually used to load data from one stream and pass work to another.
28. What is callback hell?
Callback hell also called the pyramid of doom, is the result of heavily nested, unreadable, and unmanageable callbacks, making code difficult to read and debug.
Improper implementation of asynchronous logic causes callback hell.
29. What is the reactor pattern in Node.js?
The reactor pattern is an idea of non-blocking I/O operations. This pattern delivers a handler that is associated with each I/O operation. Once an I/O request is generated, it is sent to the demultiplexer
30. Explain why Express' and 'server' applications must be separated.
Express' and 'server' applications must be separated, as this separates the API declaration from the network-related configuration, which benefits in the following ways:
" It allows in-process API testing without having to make network calls
" Faster execution of testing
" Get broader code coverage metrics
" It will enable the same API to be deployed under flexible and different network conditions
" Better separation of interests and cleaner code
Winding Up!
In this blog, we have seen the 30 best interview questions for Node.js. We hope this helps you in your learning.
