This blog on Top 50 React Interview Questions is the perfect guide for you to learn all the concepts required to clear a React interview.
What is React? What are the features of React? List some of the major advantages of React. What are the limitations of React? What is JSX? What do you understand by Virtual DOM? Explain its working. How is React different from Angular? Unique features like Virtual DOM and reusable components grab the attention of front end developers. Check out the belo2w graph which shows the trend of popular JS frameworks:.
For your ease of access, I have categorized the React interview questions namely:. This makes the HTML file really easy to understand. This file makes applications robust and boosts its performance. Below is an example of JSX:. It is a node tree that lists the elements, their attributes and content as Objects and their properties. This Virtual DOM works in three simple steps. Syntax has changed from ES5 to ES6 in following aspects:. These components split up the entire UI into small independent and reusable pieces.
Then it renders each of these components independent of each other without affecting the rest of the UI. It returns a single React element which is the representation of the native DOM component. This function must be kept pure i. Props is the shorthand for Properties in React.
They are read-only components which must be kept pure i. They are always passed down from the parent to the child components throughout the application. A child component can never send a prop back to the parent component. This help in maintaining the unidirectional data flow and are generally used to render the dynamically generated data.
States are the heart of React components. States are the source of data and must be kept as simple as possible. Basically, states are the objects which determine components rendering and behavior. They are mutable unlike the props and create dynamic and interactive components.
They are accessed via this.What are the advantages and disadvantages of using one or the other? Include notes about default props, initial state, PropTypes, and DisplayName. Invoking thing. Autobinding automatically binds our functions to the React Component instance so that passing the function by reference in the render works seamlessly. Many React utility libraries on npm provide a single function to bind all handlers in the constructor, just like React does.
See how the type is a string? One thing to note is that the type so far has just been a string. When a React Element is made from a custom Component like Comments abovethe type is a function:. What sort of tools might you use in the build steps to optimize the compiled output React code? After this occurs, the build tool is configured to carry out a group of sequential or parallel tasks.
For React, there are specific build tool plugins, such as the babel-react-optimize presets that involves compiling code into a format that optimizes React, such as automatically compiling any React. Having a strong understanding of how these fit together — and how setState or forceUpdate affect the lifecycle — will help the conscious React developer build robust UIs. Modularity is — in effect — something partially done with intention while coding, and partially done when refactoring afterwards.
Creating anonymous classes would help here, because then Loggable would not have to extend Loadable and onKeypress. There are similar implementations of mixin available on npm, using packages like react-mixin and es6-react-mixins. Recently, React provided support for — and documented its preference of — React Components declared with ES6 classes. ES6 classes allow us to create component heirarchies with less code, however this makes it more difficult to create a single Component that inherits properties from several mixins, instead forcing us to create prototype chains.
Keys themselves should be a unique number or string; so if a React Component is the only child with its key, then React will repurpose the DOM Element represented by that key in future calls to render.Level up your coding and interview skills Coderbyte is the 1 website for technical interview prep and coding challenges.
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It was an invaluable resource, thank you. Seamless Coding Environment A full-screen editor hosted on our platform to help you easily solve our challenges and practice. Solution Guides With a Coderbyte membership subscription, you'll have access to over 1 million solutions from other developers.
Improve your skills by learning how other people solved the same challenges as you. Progress Reports See how you're progressing with every challenge you complete. You'll be awarded points, badges, and you'll start ranking up against the other developers as you solve more challenges.
Once you're ready to hire a React developer, here are essential interview questions to ask and some advanced concepts to know. Before we dive right into the questions, it needs to be said that technical interviews are notorious for gotcha-style questions and irrelevant whiteboarding exercises.
This article avoids that interview style entirely — rather, I outlined five general yet vital concepts which I believe any seasoned React developer should know.
Over the years, I have been in countless interviews as both the applicant and the conductor. My experience has taught me that the best candidates for an engineering role are those who can articulate intelligent opinions and defend them using examples from their own experience.
Therefore it has no opinions on the other pieces of your technology stack and can be seamlessly integrated into any application. The answer to this question will likely vary depending on the candidate's personal experiences. The important thing is to listen for real-life examples provided and opinions on whether or not the candidate prefers React and why.
5 Essential React.js Interview Questions and Answers
I recently migrated an application originally written in AngularJS to React, and one of the things I loved most was…. By comparing and contrasting React with another library, not only can the candidate demonstrate a deep understanding of React, but also position themself as a potentially strong candidate.
One of the most valuable parts of React is its component lifecycle — so understanding exactly how components function over time is instrumental in building a maintainable application.
At the highest level, React components have lifecycle events that fall into three general categories:. Every React component defines these events as a mechanism for managing its properties, state, and rendered output. Some of these events only happen once, others happen more frequently; understanding these three general categories should help you clearly visualize when certain logic needs to be applied.
For example, a component may need to add event listeners to the DOM when it first mounts. However, it should probably remove those event listeners when the component unmounts from the DOM so that irrelevant processing does not occur. Within these three general buckets exist a number of specific lifecycle hooks — essentially abstract methods — that can be utilized by any React component to more accurately manage updates.
Understanding how and when these hooks fire is key to building stable components and will enable you to control the rendering process improving performance. Take a look at the diagram above. For example, components will automatically re-render themselves any time their properties or state change.
This is certainly true. Having said that, many React developers prefer to use JSX as its syntax is far more declarative and reduces overall code complexity. Facebook certainly encourages it in all of their documentation!A great way to improve your skills when learning to code is by solving coding challenges.
Solving different types of challenges and puzzles can help you become a better problem solver, learn the intricacies of a programming language, prepare for job interviews, learn new algorithms, and more. Below is a list of some popular coding challenge websites with a short description of what each one offers.
TopCoder is one of the original platforms for competitive programming online. It provides a list of algorithmic challenges from the past that you can complete on your own directly online using their code editor. Their popular Single Round Matches are offered a few times per month at a specific time where you compete against others to solve challenges the fastest with the best score. The top ranked users on TopCoder are very good competitive programmers and regularly compete in programming competitions.
The top ranked user maintains his own blog titled Algorithms weekly by Petr Mitrichev where he writes about coding competitions, algorithms, math, and more. The challenges range from easy finding the largest word in a string to hard print the maximum cardinality matching of a graph. They also provide a collection of algorithm tutorialsintroductory videos, and interview preparation courses.
Unlike HackerRank and other similar websites, you are able to view the solutions other users provide for any challenge aside from the official solutions posted by Coderbyte. Project Euler provides a large collection of challenges in the domain of computer science and mathematics. The challenges typically involve writing a small program to figure out the solution to a clever mathematical formula or equation, such as finding the sum of digits of all numbers preceding each number in a series.
You cannot directly code on the website in an editor, so you would need to write a solution on your own computer and then provide the solution on their website. You can solve all the challenge directly online check out this example. They provide a discussion and leaderboard for every challenge, and most challenges come with an editorial that explains more about the challenge and how to approach it to come up with a solution.
Aside from the editorial, you cannot currently view the solutions of other users on HackerRank. HackerRank also provides the ability for users to submit applications and apply to jobs by solving company-sponsored coding challenges.
CodeChef is an Indian-based competitive programming website that provides hundreds of challenges. You are able to write code in their online editor and view a collections of challenges that are separated into different categories depending on your skill level check out this example. After picking a language that you'd like to master, you tackle the coding challenges right on your machine Exercism has their own command line interface that you can download from GitHub.
It is a bit different from other challenge websites, however, because you work with a mentor after completing each challenge. The mentor reviews your answers online and helps you improve them if needed. Once your answers have been approved and submitted, you unlock more challenges. Codewars provides a large collection of coding challenges submitted and edited by their own community.
You can solve the challenges directly online in their editor in one of several languages. You can view a discussion for each challenges as well as user solutions. You can solve the challenges directly online in one of 9 programming languages.The question, "How do you or did you handle a challenge?
On the other hand, there are multiple ways to handle a challenge. One company might prefer an employee who takes a measured, methodological, and planned approach, whereas another organization might prefer individuals who dive in and do all they can to meet the challenge, without necessarily thinking of the bigger picture.
Every employee will face challenges from time to time. With this question, interviewers want to get a sense of your approach. Depending on the office culture, some approaches will make more sense than others.
Step 1: Recall a challenge that was significant, but one that you consider a success. You also want to be able to define how you met the challenge successfully.
Use specifics to describe what you did to contribute to the solution.Top 10 css interview questions and answers
Employers want to hire individuals who can turn challenges into opportunities. When brainstorming an answer, think about ways to emphasize how you made the most of a difficult time.
It is possible to learn from your hardships, and then apply what you learned to future challenges. During a difficult financial period, I was able to satisfactorily negotiate repayment schedules with multiple vendors.
From this experience, I learned the importance of thinking outside the box while solving a problem. I also learned the importance of developing and maintaining good relationships with vendors. Why It Works: This response clearly lays out how the candidate was able to meet this challenge.
Plus, this response also highlights new abilities and know-how gained in response to this challenge. We were able to successfully troubleshoot the issues and solve the problems, within a very short period of time, and without completely burning out our team. Why It Works: This answer highlights two qualities that are often very important to employers: staying on schedule, and motivating employees. If this response had stopped at the first sentence, it would be vague—those extra details on the "how" of tackling this challenge make such a difference in this answer's power.
A long-term client was about to take their business to a competitor. I met with the customer and was able to change how we handled the account on a day-to-day basis, in order to keep the business. From this situation, I learned the importance of being mindful of client relations and operations, not just after issues arise, but for the duration of the relationship.
As a result, other account managers have adopted my check-in and management processes, and have also seen improved results with their accounts.
Why It Works: Not only did this candidate learn a meaningful strategy, but the person also shared the information widely rather than hoarding it. This answer makes it clear how valuable the employee would be to his or her team.
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