Node JS Interview Questions
What is Node.js?
Node.js is an open-source, server-side JavaScript runtime environment built on Chrome’s V8 JavaScript engine. It allows developers to run JavaScript on the server-side to build scalable, high-performance web applications.
What are the advantages of using Node.js?
Node.js offers several advantages, including:
- High performance and scalability
- Event-driven architecture
- Support for real-time applications
- Large and active community
- Rich ecosystem of libraries and modules
- Easy to learn and use
What is NPM?
NPM (Node Package Manager) is the default package manager for Node.js. It provides a command-line interface for installing, managing, and sharing packages (libraries and modules) with other developers.
What is the difference between Node.js and AngularJS?
Node.js is a server-side runtime environment for executing JavaScript, while AngularJS is a front-end JavaScript framework for building dynamic web applications.
What is an event loop in Node.js?
The event loop is a mechanism in Node.js that allows it to handle asynchronous operations in a non-blocking way. It keeps track of all the asynchronous operations and executes their callbacks when the corresponding events occur.
What is a callback function in Node.js?
A callback function is a function that is passed as an argument to another function and is executed when the main function completes its task. In Node.js, callbacks are commonly used to handle asynchronous operations such as reading or writing files, making HTTP requests, or querying a database.
What is a Promise in Node.js?
A Promise is an object that represents the eventual completion or failure of an asynchronous operation. It allows you to handle asynchronous operations in a more readable and synchronous way, using the then() and catch() methods.
What is the role of REPL in Node.js?
REPL (Read-Eval-Print-Loop) is a built-in command-line interface in Node.js that allows you to execute JavaScript code interactively. It allows you to quickly test and experiment with code, and can also be used for debugging.
What is the purpose of the “require” function in Node.js?
The require function is used to import external modules (libraries or modules) in Node.js. It allows you to use code from other modules in your application and helps to keep your code modular and maintainable.
What is the difference between module.exports and exports in Node.js?
In Node.js, module.exports and exports are both used to export modules from a file. However, module.exports is the actual object that is exported, while exports is just a shorthand notation for module.exports. If you assign a new value to exports, it will no longer reference the same object as module.exports.
What is middleware in Node.js?
Middleware is a function that is executed between the server receiving a request and sending a response. It can be used to perform various tasks such as logging, authentication, error handling, or modifying the request or response objects.
What is the purpose of the “process” object in Node.js?
The process object is a global object in Node.js that provides information about the current Node.js process and allows you to control it. It can be used to retrieve environment variables, set up event listeners, or terminate the process.
What is the difference between synchronous and asynchronous code in Node.js?
Synchronous code is executed in a blocking way, which means that the program will wait until each line of code is executed before moving on to the next line. Asynchronous code is executed in a non-blocking way, which means that the program will not wait for each line of code to complete before moving on to the next line. Instead, it will execute the code in parallel and execute the callback function when the corresponding event occurs.
What is a stream in Node.js?
A stream is a mechanism in Node.js that allows you to read or write data in chunks (streams) instead of loading it all into memory at once. It is particularly useful for handling large files or real-time data such as audio or video streams.
What is clustering in Node.js?
Clustering is a technique in Node.js that allows you to run multiple instances (workers) of the same application on multiple CPU cores to improve performance and scalability.
What is the purpose of the “fs” module in Node.js?
The “fs” module in Node.js provides an API for interacting with the file system. It allows you to read or write files, create or delete directories, or perform other file-related operations.
What is the purpose of the “http” module in Node.js?
The “http” module in Node.js provides an API for creating HTTP servers and clients. It allows you to handle HTTP requests and responses, create web applications, or make HTTP requests to other servers.
What is the purpose of the “net” module in Node.js?
The “net” module in Node.js provides an API for creating TCP servers and clients. It allows you to handle low-level network connections, create real-time applications, or connect to other servers.
What is the purpose of the “crypto” module in Node.js?
The “crypto” module in Node.js provides an API for performing cryptographic operations such as hashing, encryption, or decryption. It allows you to secure your data or communications using various algorithms.
What is the purpose of the “os” module in Node.js?
The “os” module in Node.js provides an API for interacting with the operating system. It allows you to retrieve information about the system, such as the CPU, memory, or network interfaces.
What is the purpose of the “child_process” module in Node.js?
The “child_process” module in Node.js provides an API for creating child processes. It allows you to execute external commands, spawn child processes, or communicate between processes.
What is the purpose of the “cluster” module in Node.js?
The “cluster” module in Node.js provides an API for creating a cluster of workers to handle incoming connections. It allows you to distribute the workload across multiple CPU cores and improve performance.
What is the purpose of the “events” module in Node.js?
The “events” module in Node.js provides an API for creating and handling events. It allows you to create custom events and event listeners, and emit events in your application.
What is the purpose of the “url” module in Node.js?
The “url” module in Node.js provides an API for parsing and formatting URLs. It allows you to extract information from a URL, such as the hostname, pathname, or query parameters.
What is the purpose of the “path” module in Node.js?
The “path” module in Node.js provides an API for working with file paths. It allows you to manipulate file paths, resolve relative paths, or normalize paths across different platforms.
What is the purpose of the “querystring” module in Node.js?
The “querystring” module in Node.js provides an API for parsing and formatting query strings. It allows you to extract data from a query string, or generate a query string from an object.
What is a JWT in Node.js?
JWT stands for JSON Web Token, and it is a compact, URL-safe means of representing claims to be transferred between two parties. In Node.js, the “jsonwebtoken” module is commonly used to generate and verify JWTs.
What is middleware in Node.js?
Middleware is a function that sits between the request and response of an HTTP request in Node.js. It can be used to modify the request or response, or to perform additional processing before or after the request is handled.
What is the difference between “require” and “import” in Node.js?
“require” is a function used to load modules in Node.js, while “import” is a syntax used to load modules in ECMAScript modules. “require” is a commonjs syntax while “import” is an ES6 syntax. However, Node.js supports both “require” and “import”.
How can you handle errors in Node.js?
There are several ways to handle errors in Node.js, including using try-catch blocks, using the “error” event of a stream, or using a middleware function to handle errors globally. The “console.error()” method can also be used to log errors to the console.
How can you debug a Node.js application?
Node.js provides several built-in debugging tools, including the “debugger” statement, the Node.js debugger (via the command line), and third-party tools such as Visual Studio Code. The “console.log()” method can also be used for basic debugging.
What is npm in Node.js?
npm (short for Node Package Manager) is a package manager for Node.js. It allows you to install, manage, and share packages (libraries) of code with other developers.
What is a package.json file in Node.js?
A package.json file is a JSON file that contains metadata about a Node.js project, including the project’s name, version, dependencies, and other configuration options. It is used by npm to manage packages and project dependencies.
What is the purpose of the “module.exports” object in Node.js?
The “module.exports” object in Node.js is used to export functions, objects, or values from a module so that they can be used in other modules. It is a way to share code between modules in Node.js.
What is the purpose of the “process” object in Node.js?
The “process” object in Node.js provides information about the current Node.js process, such as the command line arguments, environment variables, or exit status. It also allows you to interact with the process, such as sending signals or exiting the process.
What is a callback function in Node.js?
A callback function in Node.js is a function that is passed as an argument to another function and is executed when the corresponding event occurs. It is commonly used in Node.js for handling asynchronous operations.
What is the difference between synchronous and asynchronous code in Node.js?
Synchronous code in Node.js is executed in a sequential order, blocking the execution of the next line until the current line has completed. Asynchronous code, on the other hand, does not block the execution of the next line and instead executes the code in parallel, using callbacks or promises to handle the results.
What is a Promise in Node.js?
A Promise in Node.js is an object that represents a value that may not be available yet, but will be resolved in the future (either successfully or with an error). Promises are commonly used in Node.js for handling asynchronous operations and avoiding callback hell.
What is the purpose of the “async/await” syntax in Node.js?
The “async/await” syntax in Node.js provides a more readable and concise way of writing asynchronous code by allowing developers to write code that looks synchronous but behaves asynchronously. It is built on top of Promises and provides a way to write asynchronous code that is easier to read and maintain.
What is the difference between “setImmediate” and “setTimeout” in Node.js?
“setImmediate” and “setTimeout” are both used in Node.js to execute code after a certain amount of time. The main difference between them is that “setImmediate” is executed immediately after the current event loop, while “setTimeout” is executed after a specified delay (in milliseconds).
How can you handle multiple requests in Node.js?
In Node.js, multiple requests can be handled by creating multiple processes (using the “cluster” module), using a load balancer, or by using a scalable architecture such as microservices.
What is the difference between a stream and a buffer in Node.js?
A stream in Node.js is a sequence of data that is processed piece by piece, rather than all at once. A buffer, on the other hand, is a temporary storage area for data. Streams are used in Node.js for handling large amounts of data or for processing data in real-time, while buffers are used for small amounts of data.
What is the purpose of the “cluster” module in Node.js?
The “cluster” module in Node.js is used to create multiple worker processes (or child processes) that can share the same port and handle incoming requests in parallel. It is commonly used in Node.js to improve the performance and scalability of web applications.
What is a child process in Node.js?
A child process in Node.js is a separate process that is spawned from the main Node.js process. Child processes are commonly used in Node.js to handle heavy computational tasks or to interact with other programs.
What is the difference between a “stream.write” and a “stream.end” in Node.js?
“stream.write” is used to write data to a stream, while “stream.end” is used to signal the end of a stream. When “stream.end” is called, the stream will close and no more data can be written to it.
What is the difference between “process.nextTick” and “setImmediate” in Node.js?
“process.nextTick” is used to schedule a function to be executed on the next pass of the event loop, while “setImmediate” is used to execute a function on the next iteration of the event loop, after I/O events have been processed.
What is a template engine in Node.js?
A template engine in Node.js is a tool that allows developers to create dynamic HTML templates that can be used to generate HTML pages dynamically. Popular template engines in Node.js include Handlebars, EJS, and Pug.
What is the difference between “npm install” and “npm ci” in Node.js?
“npm install” is used to install all the dependencies listed in the package.json file, while “npm ci” is used to install the exact dependencies specified in the package-lock.json file. “npm ci” is often used in automated builds to ensure that the same dependencies are installed every time.
What is the purpose of the “os” module in Node.js?
The “os” module in Node.js provides information about the operating system, such as the CPU architecture, memory usage, or network interfaces. It can be used in Node.js to write cross-platform code that works on different operating systems.
What is a router in Node.js?
A router in Node.js is a middleware that is used to handle HTTP requests based on their URL and HTTP method. It is used to create routes that map to different endpoints in a web application, and to define how those routes should handle incoming requests. Popular routers in Node.js include Express.js and Koa.js.
