MEAN Stack Interview Questions

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Last Updated: May 16, 2018

If you're looking for MEAN Stack Interview Questions for Experienced or Freshers, you are at right place. There are lot of opportunities from many reputed companies in the world. Mean stack is a combined program of MongoDB, AngularJS, Express.JS, and Node.js. So, You still have opportunity to move ahead in your career in JavaScript. Mindmajix offers Advanced MEAN Stack Interview Questions 2018 that helps you in cracking your interview & acquire dream career as MEAN Stack Developer.

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Q1) Define Node.Js?
It is a JavaScript based platform or runtime, which is built on the Chrome's V8 JavaScript engine. It is a single threaded program which employs the concurrency models that are based on the event loop. Instead of blocking the execution, it registers a callback which allows the applications to run. So, as per it, Node.js can handle all these concurrent operations without making multiple thread execution which can be scaled pretty well. 

Along with JavaScript, it uses C and C++. These are used for interacting with the file system. Then, they are started using servers that are based on HTTP or TCP. Because of its rapidly growing popularity, it is now the most common platform for cross-platform or open platform apps. With the help of this, you can develop fast and scalable network apps that can be run smoothly on Linux, Microsoft Windows, or OSX.

Q2) Define the key features of Node.JS
Asynchronous event-driven IO helps synchronic request handling. All the apps of Node.js are unit asynchronous. This means that in case a Node receives a call for participation for a few Output/Input operations, it’ll execute that operation within the background and continue with the process of different requests. So it'll not await the response from the previous requests.

1. Fast in Code execution – Node.js runs on the V8 JavaScript Runtime engine, it is the same engine that is used by Google Chrome. The node contains a wrapper over the JavaScript engine which makes the engine runtime abundant quicker and thence process of requests at intervals Node.js conjointly become quicker.

2. Single threads are however extremely ascendible – Node.js uses one thread model for the event process. The responses of these events might or might not reach the server at once. However, this doesn't block different operations which help to create Node.js extremely scalable. Ancient servers produce restricted threads for handling requests whereas Node.js creates one thread that gives service to sufficient larger numbers of such requests.

3. Library Java Script is used by Node.js – It is often another important side of the Node.js from the developer's purpose of reading. This bulk of developer areas unit already is well-versed with JavaScript. Hence, development of the Node.js becomes easier for the developer of the agency who is aware of JavaScript.

4. No Buffering – Node.js applications don't buffer any knowledge. They merely output the information in chunks.

Q3) Justify when will we decide when To Use Node.Js and when not to use it
It's ideal to use Node.js for developing streaming or event-based period applications that need less C.P.U. Usage like.

  1. Chat applications.
  2. Game servers
  3. Good for A cooperative atmosphere.

It is appropriate for environments wherever many folks work along. For instance, they post their documents; modify them by doing check-out and arrival of those documents.

Node.js supports such things by making a happening loop for each amendment created to the document. The “Event loop” feature of Node.js allows it to handle multiple events at the same time while not obtaining blocked.

1. Good for a cooperative atmosphere

It is appropriate for environments wherever many folks work along. For instance, they post their documents, modify them by doing check-out and arrival of those documents.

Node.js supports such things by making an occurrence loop for each amendment created to the document. The “Event loop” feature of Node.js permits it to handle multiple events at the same time while not obtaining blocked.

2. Servers dedicated for advertisement.

Again, we have got servers that are dedicated to handle thousands of requests which can be used for downloading the advertisements from the central host and the perfect answers for handling these tasks are Node.JS.

3. Servers dedicated for streaming.

Another ideal situation to use Node.js is for the multimedia system streaming servers wherever shopper fireplace request’s towards the server which is used to transfer totally different multimedia system contents from it.

Summarizing the whole, using Node.js is a smart choice, after you want high levels of concurrency, however, less quantity of dedicated C.P.U. Time.

Last however not the smallest amount, since Node.js uses JavaScript internally, therefore it fits best for building client-side applications that additionally use JavaScript.

4. When Node.js shouldn’t be used?

Node.js can be used for the spread of applications. However, it's one rib framework. Therefore we shouldn’t be using it for cases wherever the appliance needs a long interval. In case the server is performing some calculation, at that time it won't be allow to method the other requests. So, Node.js is the best option once when there is a process that wants less dedicated C.P.U. Time.

Q4) What are the IDEs which can be used for Node.JS development?
The most common types of IDE’s that can be used for Node.JS development applications are:

1. Cloud9
2. JetBrainsWebStorm
3. JetBrainsInteliJ IDEA
4. Komodo IDE
5. Eclipse
6. Atom

These are the best IDE’s which you can use for developing Node.JS programs. Each of them is top choices of IDEs which can be used for developing Node.js.

Q5) How can you assess REPL and Node.Js?
REPL is an acronym for Read Eval Print Loop. It also assesses datasets and lastly depicts the findings. It is important to note that REPL provides a climate which is quite similar to a Linux Shell. REPL is associated with the execution of the below-mentioned tasks.

1. Print: It is associated with printing the results that are derived from the command.

2. Read: It is associated with reading the inputs provided by the user. After the reading is complete, the places the readings into the Data structure of JavaScript. Subsequently, it stores the structure inside the function.

3. Loop: It would continue to twist the command unless the user makes use of Ctrl+C.

Q6) Is Node.Js wholly based on a single thread?
Yes, Node.js can be wholly based on a single thread. However, you should be well aware of the fact that it is just a theory behind the design of Node.Js. Apart from being involved in the process of single thread mechanism, it also makes use of callbacks and events to cater to a large number of demands. It is also vital for you to note that Node.Js possesses an optimized design. This streamlined design allows it to use both C++ and JavaScript resulting in maximum performance. The JavaScript gets executed at the side of the server. On the other hand, the C++ library ensures the processing of non-sequential I/O with the help of background workers.

Q7) Give a brief on the working mechanism of Node.Js
It is interesting to note that a Node.Js application facilitates the creation of a single thread when it is activated. Whenever the Node.Js receives a request, it first completes the processing before moving onto the next request processing. It is also important to mention here that Node.Js works by using the event loop. It also uses call back functions and handles multiple requests that are coming from the user. In the working procedure of Node.Js, an event loop always plays an essential role. An event loop is also known as a function which instigates all the event handlers. Hence, lots of works are done on the back-end. It is also important to note that while processing a request, Node.Js usually attaches a call back function. When the response is ready, the event triggers the callback function to send the response to the queries of the user.

Q8) Define the feature of call back from the perspective of Node.Js
Node.Js makes extensive use of callbacks which enables it to trigger it at the execution of a given task. In this context, it is important to note that a majority of the APIs of the Node.Js are written in such a manner that it supports the feature of call backs. Once the file read procedure gets completed, it would ask the call back function and can pass the contents of the file. Hence, it is evident that there is no wait or blocking due to the existence of the File I/O. This is the reason that the Node.js can be highly scalable as it is involved in processing a higher number of requests without waiting for the function to give back the result that is expected.

Q9) Shed light on the differences between AJAX, Node.Js and J Query
There is only one common ground that exists between AJAX, JQuery and Node.Js. It is in the form of the fact that they are the progressive execution of the JavaScript. But is it is also essential for you to note that they serve different purposes? 


It is also known as technique which comes from the client side and is mainly intended for depicting the substances of a sheet without stimulating the page. It is interesting to note that there are some significant companies which use AJAX like Stack Overflow and Facebook. The use it to depict active content.

2. Node.Js

It is also known as a server based stage which is extensively used to develop the applications. You can cite an example in this context. For instance, if you are on the lookout to figure an online worker running scheme, then you cannot design it using a JS that is from the side of the client. However, you can use the Node.Js because it goes on the server like Apache.

3. JQuery

This is a favorite JavaScript component which balances AJAX and looping. It is that kind of a library which delivers many valuable and practical functions in the development of JavaScript. It also has the unique feature of maintaining compatibility across a plethora of browsers. This ensures that it can be used to build highly responsive web applications.

Q10) Define Event Emitter of Node.js
The event module present in the Node.Js would allow you to create and manage custom events. In this context, it is important to note that the event module comprises of the class of game emitter that can be used to handle and raise custom events. You should also be aware of the fact that when an event emitter comes across an error, it usually emits an error event. On the other hand, when a new user gets added, it sends out a demonstration by the name of a new user. Moreover, when the new user gets removed, it sends a demonstration by the name of remote user.

Q11) What do you mean by NPM of Node.js?
The full form of NPM is Node Package Manager. It is associated with the two main functionalities which are listed below:

1. It usually works as a command line utility to install the packages. It also carries out version management and dependency management of various Node.Js packages.
2. It also works as an online repository in the case of Node.Js packages. These are also present in the .org file of Node.Js.

Apart from the questions mentioned above, always take into account the multi-core platforms of the Node.Js architecture. You also have to take into account the callback handler so that you can excel in the interview session.

Q12) What does it signify "non-obstructing" in node.js?
In node.js "non-blocking" implies that its IO is non-blocking. Hub utilizes "libuv" to deal with its IO in a stage rationalist manner. On windows, it utilizes finish ports for UNIX it utilizes epoll or kqueue and so on. Along these lines, it makes a non-blocking demand and upon a demand, it lines it inside the occasion circle which call the JavaScript 'callback' on the fundamental JavaScript string.

Q13) What is the type of request that is utilized as a part of node.js to import outside libraries?
Summon "require" is utilized for bringing in outer libraries, for instance, "var http=require ("http")". This will stack the http library and the single sent out protest through the http variable.

Q14) Say the structure most regularly utilized as a part of node.js
"Express" is the most well-known structure utilized as a part of node.js

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Q15) What are the upsides and downsides of Node.js?


a) If your application does not have any CPU concentrated calculation, you can construct it in JavaScript through and through, even down to the database level in the event that you utilize JSON stockpiling object DB like MongoDB.
b) Crawlers get a full-rendered HTML reaction, which is significantly more SEO well disposed instead of a solitary page application or a web sockets application keep running over Node.js.


a) Any concentrated CPU calculation will square node.js responsiveness, so a strung stage is a superior approach.
b) Using social database with Node.js is viewed as less good

Q16) What is an occasion circle in Node.js?
To process and handle outside occasions and to change over them into callback summons an occasion circle is utilized. Along these lines, at I/O calls, node.js can change starting with one demand then onto the next.

Q17) What is the upside of utilizing node.js?

a) It gives a simple method to construct adaptable system programs
b) Generally quick
c) Great simultaneousness
d) Asynchronous everything
e) Almost never pieces

Q18) What are the two sorts of API works in Node.js?
The two kinds of API works in Node.js are

a) Asynchronous, non-blocking capacities
b) Synchronous, blocking capacities

Q19) What are the Challenges with Node.js?
Accentuating on the specialized side, it's a touch of test in Node.js to have one process with one string to scale up on multi centre server.

Q20) What does it signify "non-hindering" in node.js?
In node.js "non-blocking" implies that its IO is non-blocking. Hub utilizes "libuv" to deal with its IO in a stage sceptic way. On windows, it utilizes fulfilment ports for UNIX it utilizes epoll or kqueue and so forth. In this way, it makes a non-blocking demand and upon a demand, it lines it inside the occasion circle which calls the JavaScript 'callback' on the fundamental JavaScript string.

Q21) What is node.js?
Node.js is a Server side scripting which is utilized to construct adaptable projects. Its various favorable circumstances over other server side are dialects, the noticeable being non-blocking I/O.

Q22) How node.js functions?
Node.js takes a shot at a v8 situation, it is a virtual machine that uses JavaScript as its scripting dialect and accomplishes high yield by means of non-blocking I/O and single strung occasion circle.

Q23) What do you mean by the term I/O?
I/O is the shorthand for information and yield, and it will get to anything outside of your application. It will be stacked into the machine memory to run the program, once the application is begun.

Q24) What does occasion driven programming mean?
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 system partitioned into two areas 1) Event Selection 2) Event Handling

Q25) Where would we be able to utilize node.js?
Node.js can be utilized for the accompanying purposes

a) Web applications (particularly constant web applications)
b) Network applications
c) Distributed frameworks
d) General reason applications

Q26) What's a test pyramid? By what method may you complete it while talking about HTTP APIs?
A test pyramid depicts that when works test cases there should be essentially more low-level unit tests than strange state end-to-end tests.

While talking about HTTP APIs, it may come down to this:

1. A lot of low-level unit tests for your models
2. Less joining tests, where your test how your models team up with each other
3. Essentially less affirmation tests, where you test the certifiable HTTP endpoints

Q27) Why are reliable styles essential and what apparatuses can be utilized to guarantee it?
Reliable style helps colleagues alter extends effortlessly without getting used to another style inevitably. Instruments that can help incorporate Standard and ESLint.

Q28) What is the contrast amongst AngularJS and Node.js?
Angular.JS is a web application improvement structure while Node.js is a runtime framework.

Q29) What Is Mongoose?
Mongoose is an Object Document Mapper (ODM). This implies Mongoose enables you to characterize objects with a specifically pattern that is mapped to a MongoDB archive.

Q30) What's the MEAN Stack?
The notion of MEAN stack alludes to the collection of advancements that are JavaScript based. These are also used to create web applications. MEAN is the abbreviation for ExpressJS, AngularJS MongoDB and Node.js. From customer to server to database, MEAN is full stack JavaScript.

Q31) What is express?
Express is one the most pervasive and by and large used web frameworks in Node.js headway zone. Express is an insignificant web server in view of Node.js that gives all the essential value required for passing on web applications to the program and PDAs. ExpressJS empowers you to manage Routes, Server, and I/O stuff easily.

Q32) Utilize Mettl Assessment for MEAN Stack Developer for enrolment and enlisting:
MEAN is a web-pile of JavaScript innovations that aid in growing speedier web applications and dynamic sites. A decent MEAN Stack Developer has amazing learning of back-end dialects and can compose clean codes for making web applications.

Mettl Assessment for MEAN Stack Developer helps managers in enlisting applicants with 1-3 years of important work involvement. The test assesses a competitor's hands-on understanding and specialized aptitudes involving the four noteworthy segments:

1. MongoDB - CRUD Operations, Indexing, Replica Set and Shading, and so forth.
2. Express.js - Routing, Template, Scaffolding, and so forth.
3. AngularJS - Controllers, Forms Validation and SQL, Routing, and so forth.
4. Node.Js - BUFFERS AND STREAMS, File System, Node Modules, and so forth.

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Q33) What is control stream work?
A nonspecific bit of code which keeps running in the middle of a few non-concurrent work calls is known as control stream work.


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