MEAN Stack Interview Questions and Answers

1Q) What’s the MEAN Stack?

Ans: The term MEAN stack refers to a collection of JavaScript-based technologies used to develop web applications. MEAN is an acronym for MongoDB, ExpressJS, AngularJS, and Node.js. From client to server to database, MEAN is full-stack JavaScript.

2Q) What is Express?

Ans: Express is one the most prevalent and generally utilized web systems in Node.js advancement zone. Express is a negligible web server based on Node.js that gives all the basic usefulness required for conveying web applications to the program and cell phones. ExpressJS enables you to deal with Routes, Server, and I/O stuff effortlessly.

3Q) What is Node.js?

Ans: Node.js is a headless JavaScript runtime. It is literally the same JavaScript engine (named V8) that runs inside of Google Chrome, except that with Node.js, you can run JavaScript from the command line instead of in your browser.

4Q) What is DATA Modeling?

Ans: Data modeling, in the context of Mongoose and MongoDB, is defining what data can be in a document, and what data must be in a document. When storing user information you might want to be able to save the first name, last name, email address, and phone number. But you only need a first name and email address, and the email address must be unique. This information is defined in a schema, which is used as the basis for the data model.

5Q) What are the features of Node.js?

Ans: Node.js is a single-threaded but highly scalable system that utilizes JavaScript as its scripting language. It uses asynchronous, event-driven I/O instead of separate processes or threads. It is able to achieve high output via a single-threaded event loop and non-blocking I/O.

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6Q) Why is consistent style important and what tools can be used to assure it?

Ans: Consistent style helps team members modify projects easily without having to get used to a new style every time. Tools that can help include Standard and ESLint.

7Q) What is the difference between AngularJS and Node.js?

Ans: Angular.JS is a web application development framework while Node.js is a runtime system.

8Q) What Is Mongoose?

Ans: Mongoose is an Object Document Mapper (ODM). This means that Mongoose allows you to define objects with a strongly-typed schema that is mapped to a MongoDB document.

9Q) What Are The Key Features Of Node.Js?

Ans: -Asynchronous event-driven IO helps concurrent request handling – All APIs of Node.js are offbeat. This component implies that if a Node gets a demand for some Input/Output activity, it will execute that task out of sight and proceed with the preparation of different solicitations. Accordingly, it won't sit tight for the reaction from the past solicitations.

-Quick in Code execution – Node.js utilizes the V8 JavaScript Runtime motor, the one which is utilized by Google Chrome. Hub has a wrapper over the JavaScript motor which makes the runtime motor substantially quicker and thus preparing of solicitations inside Node.js additionally turns out to be speedier.

-Single-Threaded yet Highly Scalable – Node.js utilizes a solitary string model for occasion circling. The reaction from these occasions could conceivably achieve the server quickly. In any case, this does not piece different activities. In this way making Node.js exceptionally adaptable. Customary servers make restricted strings to deal with demands while Node.js makes a solitary string that gives administration to significantly bigger quantities of such demands.

-Node.js library uses JavaScript – This is another essential part of Node.js from the engineer's perspective. The larger part of engineers is now knowledgeable in JavaScript. Consequently, advancement in Node.js winds up plainly less demanding for a designer who knows JavaScript.

-There is an active and energetic group for the Node.js system – The dynamic group dependably keeps the structure refreshed with the most recent patterns in the web advancement.

-No Buffering – Node.js applications never support any information. They essentially yield the information in pieces.

10Q) Explain REPL In Node.Js?

Ans: The REPL stands for “Read Eval Print Loop”. It is a simple program that accepts the commands, evaluates them, and finally prints the results. REPL provides an environment similar to that of a Unix/Linux shell or a window console, in which we can enter the command and the system, in turn, responds with the output. REPL performs the following tasks.

READ- It Reads the input from the user, parses it into JavaScript data structure, and then stores it in the memory.

EVAL- It Executes the data structure.

PRINT- It Prints the result obtained after evaluating the command.

LOOP- It Loops the above command until the user presses Ctrl+C two times.

11Q) What Is The Difference Between Nodejs, AJAX, And JQuery?

Ans: The one common trait between Node.js, AJAX, and jQuery is that all of them are the advanced implementation of JavaScript. However, they serve completely different purposes.

Node.Js – It is a server-side platform for developing client-server applications. For example, if we're to build an online employee management system, then we won’t do it using client-side JS. But the Node.js can certainly do it as it runs on a server similar to Apache, Django not in a browser.

AJAX (Aka Asynchronous Javascript And XML) – It is a client-side scripting technique, primarily designed for rendering the contents of a page without refreshing it. There are a no. of large companies utilizing AJAX such as Facebook and Stack Overflow to display dynamic content.

JQuery –It is a famous JavaScript module that complements AJAX, DOM traversal, looping, and so on. This library provides many useful functions to help in JavaScript development. However, it’s not mandatory to use it but as it also manages cross-browser compatibility, so can help you produce highly maintainable web applications.

12Q) What's the difference between operational and programmer errors?

Ans: Operation errors are not bugs, but problems with the system, like request timeout or hardware failure.

On the other hand programmer errors are actual bugs.

13Q) What's a test pyramid? How might you actualize it when discussing HTTP APIs?

Ans: A test pyramid portrays that when works test cases there ought to be significantly more low-level unit tests than abnormal state end-to-end tests.

When discussing HTTP APIs, it might come down to this:

Plenty of low-level unit tests for your models

Less joining tests, where your test how your models collaborate with each other

Significantly fewer acknowledgment tests, where you test the genuine HTTP endpoints

14Q) Explain callback in Node.js?

Ans: A callback work is called toward the culmination of a given errand. This enables other code to keep running meanwhile and keeps any blocking. Being an offbeat stage, Node.js intensely depends on callback. All APIs of Node is composed to help callbacks.

15Q) What does event-driven programming mean?

Ans: In PC programming, occasion driven writing computer programs is a programming worldview in which the stream of the program is controlled by occasions like messages from different projects or strings. It is an application engineering method separated into two segments 1) Event Selection 2) Event Handling

16Q) Explain REPL In Node.Js?

  Ans: The REPL stands for “Read Eval Print Loop”. It is a simple program that accepts the commands,                evaluates them, and finally prints the results. REPL provides an environment similar to that of                     Unix/Linux shell or a window console, in which we can enter the command and the system, in turn,         responds with the output. REPL performs the following tasks.

     READ It Reads the input from the user, parses it into JavaScript data structure, and then stores it in the memory. EVAL It Executes the data structure. PRINT It Prints the result obtained after evaluating the command. LOOP It Loops the above command until the user presses Ctrl+C two times.

17Q) Is Node.Js Entirely Based On A Single-Thread?

 Ans:  Yes, it’s true that Node.js processes all requests on a single thread. But it’s just a part of the theory behind Node.js design. In fact, more than the single thread mechanism, it makes use of events and callbacks to handle a large no. of requests asynchronously.

       Moreover, Node.js has an optimized design that utilizes both JavaScript and C++ to guarantee maximum performance. JavaScript executes at the server-side by Google Chrome v8 engine. And the C++ lib UV library takes care of the non-sequential I/O via background workers.

      To explain it practically, let’s assume there are 100s of requests lined up in the Node.js queue. As per the design, the main thread of the Node.js event loop will receive all of them and forward to background workers for execution. Once the workers finish processing requests, the registered callbacks get notified on the event loop thread to pass the result back to the user.