MERN Stack Interview Questions and Answers | MERN Stack Interview 2023 | Simplilearn

The video introduces the MEAN stack as a popular web development stack comprising MongoDB, Express, React, and Node.js, and outlines the basic roles of each technology (MongoDB for databases, Express for backend, React for frontend, and Node.js for server-side runtime). It highlights how these technologies together create highly scalable web applications.

It informs viewers about an upcoming segment on frequently asked MEAN stack interview questions. It advises subscribing for updates and suggests a coding bootcamp for immersive learning. The bootcamp covers Java technologies, while also mentioning other topics like Angular, JSPs, and MongoDB.

The presenter explains JSX (JavaScript Syntax Extension) used in React.js to bind JavaScript and HTML, simplifying code structure. The concept of the virtual DOM in React, which allows for efficient page updates by only altering changed elements, is introduced. React extensions like Flux and React Native for mobile apps are mentioned.

The speaker discusses React components, dividing complex UIs into reusable chunks. They detail "state" in React as a way to track data changes over time, initialized in constructors, allowing pages to render based on current data states. Higher-order components and pure components, which help with reuse and shallow comparison respectively, are also described.

React routing is introduced as a means to manage URL paths and deliver components using React modules. The session transitions to a Node.js interview overview with beginner to advanced questions. Node.js is presented as a leading server-side platform due to its open-source, cross-platform JavaScript runtime allowing fast application development.

Node.js's foundation on the V8 engine, its high-speed asynchronous I/O operations, and its applications in web, distributed, and network applications are highlighted. The difference between frontend and backend development is explained, with examples of typical technologies used in each realm.

The section delves into npm (Node Package Manager), its role in managing online repositories and command line utilities. An overview of Node.js modules is given, explaining how these JavaScript libraries are utilized for server-side tasks, such as setting up a web server using HTTP.

Node.js's advantage over traditional back-end technologies like Java and PHP is discussed. Its speed, node package manager resources, suitability for real-time data applications, and ease of code synchronization between client and server due to JavaScript are noted as key benefits.

The information on Angular vs Node.js establishes Angular as a client-side framework and Node.js as a server-side one. Databases commonly used with Node.js, particularly MongoDB and MySQL, are discussed, with MongoDB being preferred for its scalability with large data sets.

The segment covers popular Node.js libraries like Express.js for quick API development and Mongoose for database connectivity. The pros (fast processing, extensive package availability) and cons (complex callback structure, CPU-intensive operations) of Node.js are examined, with solutions like cloud scaling proposed.

Commands relevant to Node.js, particularly for importing external libraries using the "require" function, are elaborated upon. The transition to intermediate Node.js questions includes explanations of event-driven programming, how event loops, emitters, and API functions operate, highlighting synchronous vs asynchronous programming.

The video explains Node.js's package.json file's role as a project metadata holder and using URL modules for utility enhancement. Express.js is detailed as a framework facilitating web app creation in Node.js, streams in Node.js accomplish ongoing data reads/writes, and dependency management is outlined.

Synchronous/non-blocking APIs in Node.js scale applications effectively by allowing data to be processed without blocking operations. Examples of using async functionality and module exports to encapsulate code for shared use are also covered.

MongoDB is introduced as a key NoSQL database, with emphasis on its document-based storage structure, scalability, and schema flexibility. Common MongoDB interview questions focus on its architecture, alternative NoSQL databases, and distinctions from SQL databases.

Details on MongoDB's data models (embedded and reference), how indexing expedites query operations, replication and sharding for data availability, and the advantages of MongoDB's flexible schema are provided. Practical questions hone in on tasks like document insertion and handling large files.