Full Stack Developer Interview Questions and Answers

Full stack development is one of the hardest to fit in technical jobs worldwide. Also, full stack developers are in great demand in leading companies. It has a great future and they get numerous opportunities. Their salary too is phenomenally high. This means an individual can be hired only after undergoing a good quality check. Companies will be very concerned about hiring somebody for this job in particular.

1.What programming languages are you comfortable working with?

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• State languages including HTML, CSS and JS. These are minimum requirements and you need to have more languages in your kitty. You can show knowledge of other languages like Python, Java, Ruby, and PHP etc.,
• Learn Python course online, learn PHP course online with Crampete to upskill yourself.

2.Your favourite language and why?

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State the language you like the most, the one you feel most comfortable in. State it’s pros and cons. Also give details on how this programming languages was used effectively by you in your work.

3.Which do you think is most important for a full stack developer?

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This is about any full stack web developer tool, technology or a skill that you feel is indispensable for a full stack web developer. Justify why you feel like that. 

4.What are you working on now?

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A good coder is always coding something or the other. Talk about your interests and other projects you are working on your own time along with your project.

5.How do you keep abreast of new developments and trends?

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Don’t throw about names that you’ve heard but know nothing about. There are new releases often and you don’t have to know everything. Learn some stuff about some recent technologies and say only those.

6.Do you work with any new technology?

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The interviewer will try to trip you up. You select the one already mentioned in the previous answer and expound on it. Don’t do in-depth lecture on the subject.

7.What language and tools will you use to develop a project from scratch?

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• This is a hypothetical question. The interviewer wants to assess you depth and insight on the complete process. Answer carefully for this question. Explain the workflow and design and your strategy to develop and complete the project. If you have worked on mobile application development with Java you can mention that as well. If you are interested in learning Java course online, check out our course page.
• If you are looking to learn skills like ReactJs, Angular.js, or other programming languages, check out our Crampete modular programs.

8.Tell me about some project you have worked on. How did you select the tools and technologies involved?

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This is a question meant for experienced candidates. Explain succinctly what process you followed, why you selected that language and those tools and technologies. Explain the problems you faced during the development and how you managed to overcome the issues.

9.How do you deal with inefficient coding turned in by your team colleague?

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Please explain in some detail about the incident, but remember to put a positive spin on it. Reinforce that you handled in a positive way and there is no resentment from the other members. Finish by stating what you learnt from the episode.

10.What would you say was your best implementation experience till date?

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Here, talk about about the project or the issue you took charge of. Give details on what technologies you used and how solved the issues. What is the learning you brought away from this is important.

11.What is multithreading?

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Improve CPU performance with multi-threading. A program can manage multiple requests with the same user and can manage many users at the same time. Multiple processes are executed at the same time to improve the performance.

12.What is continuous integration?

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Merge the working copies of all developers to one shared mainline a few times a day. This helps with easy problem detection. You should know how this works.

13.Explain CORS?

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Cross-Origin Resource Sharing known as CORS, allows you to request for different resources from a different domain outside of the domain where the resource is originally from.

14.What is Pair-programming?

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This is to check if you know the concept and feel out how you react to it. This is an agile technique where you sit down and sort through the code with another coder.

15.How to reduce load time of web application?

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Minimize HTTP requests, optimizing images, reducing redirects, enabling browser caching are some methods to reduce the load time of web apps. You should be able to describe how these techs help in reducing time effectively.

16.What is long polling?

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Long polling is a development pattern that surpasses data from server to client. When the client sends a request, and the information requested is not available, the system waits and return a response rather than sending back empty requests.

17.What is an Application server?

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An application that lets you design and maintain server side as well as client side application. This is an important concept that you need to be familiar with.

18.What is Referential transparency?

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This is a way to replace expressions in a program without impacting the final result. It is an aspect of functional programming.

19.What tools would you use to test your code’s functionality?

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Answer this according to your skills and the tools that you have previously used. Remember to explain in detail what you have used and how it solved your problems.

20.How do you keep yourself updated about the new trends in the industry?

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    This is a typical question to understand your involvement in technology. A good way to demonstrate your involvement in continuous learning would be by speaking about the community meetups you visit. You can also talk about the webinars and the forums you regularly attend. If you have personal projects on which you apply your skills, this is a good time to showcase that as well.

21.What’s the most recent thing that you have learned?

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This question is used to probe the authenticity of the information you furnished in your last question. It is important that you are aware of the latest in the industry and have a pulse of what’s happening. You might talk about a website that you tested recently, or talk about an obnoxious case study about a serious bug you recently read about. A point to note, never give the interviewer an impression that you have learned nothing in the past 6 months. This is a fast-changing tech game, and being up-to-date with the current trends is an absolute must.

22.Are you aware of design patterns?

Ans:

While answering this question you should show your ability to understand common errors that might creep in while creating web applications. If your knowledge is formal and deep, you must push the employer to gain confidence in the experience you possess in understanding a clean and readable code.  

23.Do you enjoy management or execution more?

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Every senior professional will be asked this full stack web developer interview question. Recruiters want to know if you want to stay in a technical role or would want to switch to a managerial position. They also at times might push a bit and ask if you prefer to work alone or in paired groups. It’s important, to be honest here. The company’s requirements might be different from your interests, so it is ideal that the expectations are set straight from the get-go.

24.Explain Inversion of Control?

Ans:

This question is very commonly asked to check the candidate’s understanding of design patterns. It is a broad term but is more specifically used by software developers for describing a pattern which is used to decouple layers and components in a system.

25.What is the main difference between GraphQL and REST?

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This is a moderately difficult question but a good developer would be able to get through with this in ease. An important difference between GraphQL and REST is that GraphQL doesn’t deal with dedicated resources. Everything referred to as a graph is connected and can be queried to app needs.

26.Explain what is DevOps ?

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DevOps is a newly emerging term in IT field, which is nothing but a practice that emphasizes the collaboration and communication of both software developers and other information-technology (IT) professionals. It focuses on delivering software product faster and lowering the failure rate of releases.

27.What are the success factors for Continuous Integration?

Ans:

• Maintain a code repository
• Automate the build
• Make the build self-testing
• Everyone commits to the baseline every day
• Every commit (to baseline) should be built
• Keep the build fast
• Test in a clone of the production environment
• Make it easy to get the latest deliverables
• Everyone can see the results of the latest build
• Automate deployment

28.What is the difference between “git pull” and “git fetch”? 

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In the simplest terms, git pull does a git fetch followed by a git merge.

• When you use pull, Git tries to automatically do your work for you. It is context sensitive, so Git will merge any pulled commits into the branch you are currently working in. pull automatically merges the commits without letting you review them first. If you don’t closely manage your branches, you may run into frequent conflicts.
• When you fetch, Git gathers any commits from the target branch that do not exist in your current branch and stores them in your local repository. However, it does not merge them with your current branch. This is particularly useful if you need to keep your repository up to date, but are working on something that might break if you update your files. To integrate the commits into your master branch, you use merge.

29.What is Callback Hell?

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The asynchronous function requires callbacks as a return parameter. When multiple asynchronous functions are chained together then callback hell situation comes up.

30.What is Bridge pattern?

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• Bridge pattern is used when we need to decouple an abstraction from its implementation so that the two can vary independently. This type of design pattern comes under structural pattern as this pattern decouples implementation class and abstract class by providing a bridge structure between them.
• The bridge pattern is useful when both the class and what it does vary often. The class itself can be thought of as the abstraction and what the class can do as the implementation. The bridge pattern can also be thought of as two layers of abstraction.This pattern involves an interface which acts as a bridge which makes the functionality of concrete classes independent from interface implementer classes. Both types of classes can be altered structurally without affecting each other.

31.What is Observer pattern?

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• Observer pattern (also known as Publish-Subscribe Pattern) is used when there is one-to-many relationship between objects such as if one object is modified, its dependent objects are to be notified automatically. Observer pattern falls under behavioral pattern category.
• An object with a one-to-many relationship with other objects who are interested in its state is called the subject or publisher. The observers are notified whenever the state of the subject changes and can act accordingly. The subject can have any number of dependent observers which it notifies, and any number of observers can subscribe to the subject to receive such notifications.

Observer pattern uses two actor classes:

• The Observer (os Subscriber) abstract class provides an update() method which will be called by the subject to notify it of the subject’s state change.
• The Subject (or Publisher) class is also an abstract class and defines four primary methods: attach(), detach(), setState(), and notify()

32.What’s the difference between a blue/green deployment and a rolling deployment? 

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• In Blue Green Deployment, you have TWO complete environments. One is Blue environment which is running and the Green environment to which you want to upgrade. Once you swap the environment from blue to green, the traffic is directed to your new green environment. You can delete or save your old blue environment for backup until the green environment is stable.
• In Rolling Deployment, you have only ONE complete environment. The code is deployed in the subset of instances of the same environment and moves to another subset after completion.

33.Explain a use case for Docke?

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• Docker a low overhead way to run virtual machines on your local box or in the cloud. Although they’re not strictly distinct machines, nor do they need to boot an OS, they give you many of those benefits.
• Docker can encapsulate legacy applications, allowing you to deploy them to servers that might not otherwise be easy to setup with older packages & software versions.
• Docker can be used to build test boxes, during your deploy process to facilitate continuous integration testing.
• Docker can be used to provision boxes in the cloud, and with swarm you can orchestrate clusters too.

34.Could you explain the Gitflow workflow? 

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• Gitflow workflow employs two parallel long-running branches to record the history of the project, master and develop:
• Master – is always ready to be released on LIVE, with everything fully tested and approved (production-ready).
• Hotfix – Maintenance or “hotfix” branches are used to quickly patch production releases. Hotfix branches are a lot like release branches and feature branches except they’re based on master instead of develop.
• Develop – is the branch to which all feature branches are merged and where all tests are performed. Only when everything’s been thoroughly checked and fixed it can be merged to the master.
• Feature – Each new feature should reside in its own branch, which can be pushed to the develop branch as their parent one.

35.What are the advantages and disadvantages of using “use strict”? What are the advantages and disadvantages of using “use strict”?

Ans:

• ‘use strict’ is a statement used to enable strict mode to entire scripts or individual functions. Strict mode is a way to opt into a restricted variant of JavaScript.

Advantages:

• Makes it impossible to accidentally create global variables.
• Makes assignments which would otherwise silently fail to throw an exception.
• Makes attempts to delete undeletable properties throw (where before the attempt would simply have no effect).
• Requires that function parameter names be unique.
• this is undefined in the global context.
• It catches some common coding bloopers, throwing exceptions.
• It disables features that are confusing or poorly thought out.

Disadvantages:

• Many missing features that some developers might be used to.
• No more access to function.caller and function.arguments.
• Concatenation of scripts written in different strict modes might cause issues.

36.What do you think of AMD vs CommonJS?

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• Both are ways to implement a module system, which was not natively present in JavaScript until ES2015 came along. CommonJS is synchronous while AMD (Asynchronous Module Definition) is obviously asynchronous. CommonJS is designed with server-side development in mind while AMD, with its support for asynchronous loading of modules, is more intended for browsers.
• I find AMD syntax to be quite verbose and CommonJS is closer to the style you would write import statements in other languages. Most of the time, I find AMD unnecessary, because if you served all your JavaScript into one concatenated bundle file, you wouldn’t benefit from the async loading properties. Also, CommonJS syntax is closer to Node style of writing modules and there is less context-switching overhead when switching between client side and server side JavaScript development.

37.What is Event Loop?

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• Node.js is a single threaded application but it support concurrency via concept of event and callbacks. As every API of Node js are asynchronous and being a single thread, it uses async function calls to maintain the concurrency. Node uses observer pattern. Node thread keeps an event loop and whenever any task get completed, it fires the corresponding event which signals the event listener function to get executed.

38.Explain the purpose of clearing floats in CSS ?

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• The clear CSS property specifies whether an element can be next to floating elements that precede it or must be moved down (cleared) below them.
• Clearing floats (or clearfixing) basically forces the containing element to expand to contain its child elements. It thus forces the subsequent elements to appear below it.

39.Are there any disadvantages to GraphQL? 

Ans:

Disadvantages:

• You need to learn how to set up GraphQL. The ecosystem is still rapidly evolving so you have to keep up.
• You need to send the queries from the client, you can just send strings but if you want more comfort and caching you’ll use a client library -> extra code in your client
• You need to define the schema beforehand => extra work before you get results
• You need to have a graphql endpoint on your server => new libraries that you don’t know yet
• Graphql queries are more bytes than simply going to a REST endpoint
• The server needs to do more processing to parse the query and verify the parameters

40.When should you NOT use arrow functions in ES6? Name three or more cases?

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Arrow functions should NOT be used:

• When we want function hoisting – as arrow functions are anonymous.
• When we want to use this/arguments in a function – as arrow functions do not have this/arguments of their own, they depend upon their outer context.
• When we want to use named function – as arrow functions are anonymous.
• When we want to use function as a constructor – as arrow functions do not have their own this.
• When we want to add function as a property in object literal and use object in it – as we can not access this (which should be object itself).

41.How can you share code between files?

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• This depends on the JavaScript environment.
• On the client (browser environment), as long as the variables/functions are declared in the global scope (window), all scripts can refer to them. Alternatively, adopt the Asynchronous Module Definition (AMD) via RequireJS for a more modular approach.
• On the server (Node.js), the common way has been to use CommonJS. Each file is treated as a module and it can export variables and functions by attaching them to the module.exports object.

42.What is the difference between directive and component?

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S.no	Directive	Component
1.	It is a behavior that has been added to the existing components.	Components have their own view i.e., HTML and styles.
2.	There can be multiple directives in one element.	There can be only one component in one element.

43.What do you mean by routing in angular js?

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If the developer wants to go through different pages in a single page application and also with no reloading of the page then the ngRoute module is used. It routes the application to different pages with the reloading of the complete application.

44.What is MEAN Stack?

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MEAN stack is a user-friendly free and open-source JavaScript software which is used for building the dynamic web sites and the web applications. The advantage of using the MEAN stack is that only language JavaScript runs on all the levels of the applications which makes it efficient.

MEAN stack is the composition of:-

• MongoDB as the database
• Express.js as the web framework which runs on Node.js
• AngularJS as the frontend framework
• Node.js as the server platform.

45.What is the difference between Nodejs, AJAX, And JQuery?

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Node.js	AJAX	JQuery
It allows JavaScript to be run without a browser	It a way for JavaScript to request the data from a server but without refreshing the page or blocking the application.	It is a JavaScript library which was built to automate and simplify the common web tasks like AJAX

46.Explain the difference between AngularJS and Node.js?

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S.no	AngularJS	Node.js
1.	Written only in Javascript.	Written in Javascript, C, C++.
2.	It is a client-side web application	It is a server-side web application
3.	It is a web application framework in itself	It is not a framework but has a framework like express.js

47.What is Node.js and why it is used?

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• Node.js is a server environment to be used for web development. Node.js is an open-source server. This is based on google chrome’s JavaScript engine V8.
• Node.js is used to create applications in less time and useful for data-intensive applications.

48.What is Express.js?

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Express.js is a web application server framework. It is used for Node.js. It helps to create node.js applications in less time. It also provides security-related help for node.js.

49.What is the difference between constructor & destructor?

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S.no	Constructor	Destructor
1.	It allocates the memory to an object.	It deallocates the memory of an object.
2.	It accepts argument.	It does not take an argument.
3.	In a class, there can be multiple constructors.	In a class, there can only be one destructor.

50.What is final class and final method?

Ans:

• Final classes cannot be subclassed; it is not open for change and can be used reliably for common execution of routines. “String” class in Java is an example of a final class. This is done for security and sometimes for efficiency.
• Final methods cannot be overridden. They are not open to change. This prevents accidental changes which may result in crashing of application.

51.What do you mean by Closures?

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A closure is the capability of an inner function to have access to variables in local scope in which internal function was created. Even if the out function has finished execution, closure means the inner function has access to its local variables.

52.What do you mean by promise?

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A Promise is an object which shows the result of the asynchronous operation. The result can be a resolved value or a reason why the process failed like “a network error occurred.

A promise can be any of the 3 states:-

• Pending – the promise’s result hasn’t yet been identified because the asynchronous operation has not been completed yet.
• Fulfilled – the asynchronous operation has completed, and the promise has now a resolved value.
• Rejected – the asynchronous operation has failed, and the promise has a reason that indicates why the process failed.

53.What is event bubbling and capturing in javascript?

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• Event Bubbling and Event Capturing are the ways of the event propagation in the HTML API when an event occurs in an element which is located inside the other part and both the parts have registered a handle with the recently happened event. Here the event propagation mode identifies that in which order the elements receive the event.
• In the case of Event Bubbling, the event is first captured and also handled by the innermost element, and then the event is propagated to the outermost element.
• In the case of Event Capturing, the event is first captured and also handled by the outermost element, and then the event is propagated to the innermost element.

54.What the differences are between == and ===?

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S.no	==	===
1.	If the variables are not of the same types, then it converts one variable type to another and performs the operation	If the variables are not of the same type, then it will not achieve the process and will return false

55.Explain the difference between horizontal scaling and vertical scaling in the database?

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S.no	Horizontal scaling	Vertical scaling
1.	More machines are added into your existing resources	More power i.e. CPU, RAM is attached to the current machine
2.	Horizontal scaling there is no limit	Vertical scaling depends on the capacity of the machine
3.	Licensing fees is more	Licensing fees is less

56.What are normalization and denormalization?

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• Normalization means merely a process of reducing or eliminating the data redundancy. As a result, space is saved, and the consistency of data is increased.
• The denormalization is an optimization process to increase the data redundancy in the database. As a result, the joins are avoided, and the performance of the database structure is improved. Denormalization is done after the normalization process

57.Explain the difference between the left join & right to join?

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S.no	LEFT JOIN	RIGHT JOIN
1.	It gets the records from the rows of the LEFT side linked table and only the matching records from the RIGHT table.	It gets the records from the rows of the RIGHT side linked table and only the matching records from the LEFT table.

58.What does acid stand for in database?

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The acronym ACID stands for Atomicity, Consistency, Isolation, and Durability.

59.What is the difference between defer and async?

Ans:

S.no	defer	async
1.	It downloads the file during the HTML parsing but executes the data after the parsing is completed.	It downloads the data during the HTML parsing, but it stops the parsing from executing the downloaded file.
2.	Defer is used when the script relies upon another script.	Async is used if the script does not rely upon any scripts.

60.What are the difference between MVP and MVC?

S.no	MVP	MVC
1.	View handles the user gestures	The controller manages the user gestures
2.	The interaction with the model is passed through the presenter	The view can query the model directly
3.	Provides full sport to unit testing	Provides limited support to unit testing

61.What is the difference between GET and POST?

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S.no	GET	POST
1.	GET is used for recovering the data	POST is mainly used for writing the data
2.	It carries the request parameter in the URL string	It takes the request parameter in the message body.
3.	It can be bookmarked	It cannot be bookmarked

62.Which is your personal favourite language?

Ans:

Rather than explaining about one favourite, full stack developers are expected to tell about most of the languages they are aware of. Since full stack developers are well-versed with both front end and back end, telling about both languages is good. Also about some basic web languages like HTML, CSS and JavaScript. They can also tell why they like popular languages namely Python, MEAN, LAMP, Ruby on Rails and many more.

63.How do you develop a successful Continuous Integration process?

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Firstly, we must maintain an idea for the code of the project. Then we must automate the build which should be self-testing. Codes should be integrated by everyone on the build every day. The build must be quick and updated according to the requirements of the production. Finally, the deployment process should be automated. With these steps, Continuous Integration can be successful in detection problems and making production quick.

64.How do you get know about the latest trends being a full stack developer?

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As a full stack developer, one should stay updated with all the latest trends. We must test on new software every now and then. We must acquire new skills and this will exhibit full stack developers as passionate, knowledgeable individuals. Reading books, blogs, attending seminars can keep us updated.

65.Tell some of the latest trends that you came to know recently?

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Some of the latest trends a full stack developer should know are about the recent introduction of more compatible extensions and about the improvements made in JavaScript programming. Today, there are several mobile applications, games and real-time applications being developed due to the Vue JavaScript Functional. Digital trends keep changing every day and for a full stack developer it is essential to be aware of most of them.