React JS is popular and growing in the field of web app development and hence there are so many career opportunities available for React JS Developer. Here we have listed top react JS interview questions with their answers for everyone.
Read: Top 20 ReactJS Interview Question and Answer for Freshers In 2020
Q1. What is React JS?
React JS is JavaScript Library developed by Facebook in 2011, to build an interactive User Interface. It is one of the most popular JavaScript frameworks of the web and mobile apps.
Q2. List the advantages of React JS
It is Easy to learn
Efficiency
Simplicity
High scalability
Increased performance
Stable code
Q3: Does ReactJS use HTML or not?
React JS does not use HTML. Instead, it uses JSX which is similar to HTML.
Q4. What is mean by JSX in React JS?
JSX is a preprocessor step which allows us to put XML/HTML syntax to JavaScript. Basically, with help of JSX one can write brief XML/HTML structure in same file of JavaScript code.
Q5. How React JS is different from Angular JS?
| Aspect | Angular JS | React JS |
| DOM | Use of Real DOM | Use of Virtual DOM |
| Data Binding | 2 way binding | 1 way binding |
| Developed by | ||
| Design | It is a complete Framework | It is JavaScript Library |
| Language | Uses Typescript – superset of JavaScript | Uses JavaScript with the extended XML syntax |
Q6. Do you know the life Cycle of ReactJS?
React Components goes through 4 phases. These are
- Initialization
- Mounting
- Updation
- Unmounting
Q7. What is mean by Flux in Java Script?
Flux is an application architecture which is used to create some data layers in JavaScript apps. It is helpful in maintaining data stream in unidirectional way.
Q8. What is the Main difference between virtual DOM and Real DOM?
Document Object Model (DOM) allows programs to access and update the structure and content of a React JS document.
- Virtual DOM updates with fast speed whereas Real DOM updates with slow speed.
- In Virtual DOM, there is no memory wastage but in Real DOM there is excess wastage of memory.
- Real DOM updates HTML Directly, Virtual DOM doesn’t update it directly.
- In Virtual DOM, manipulation of DOM is simple, easy and less costly. In Real DOM it is costly
Q9. What is mean by controlled components and uncontrolled components in React JS?
Controlled components are easier to implement so it is more advisable to use. In controlled components, form data is handled by React Components
Uncontrolled components are standby or substitute for controlled component. In this, form data is handled by DOM
Q10. What is the use of Arrow function in React JS?
Arrow functions are one of extremely important functions for React operations. Arrow functions are used to predict the behavior of bugs when passed as callbacks. Basically it is used to prevent bugs.
Q11. List some important features of ReactJS?
React is one of the best JavaScript User Interface frameworks and it comes with so many features that helps developers to create amazing application with ease. Here we are listing some features of React JS which are important in designing and development.
- It is Adaptable
- React JS is Free and Open Source
- It can be shared on Server as well as client side
- Asynchronous Functions & Generators
- Flux Library
- Destructuring Assignments
- Usage of JSX makes it easier to read and write code
Q12. What is Redux?
Redux is one of the most in-demand libraries used for front-end development. It is small in size, having no any dependencies and mainly designed for JavaScript applications and also used for managing the entire state of an app. Redux builds such applications which are simple for deployment in various environments and easy to test.
Q13. What is ref in ReactJS and where it is used?
ref is used for storing the reference of component which is returned by the component render() configuration function. Refs can be used in the cases such as:-
Text selection
Media playback
Triggering animations.
Integration with 3rd party DOM libraries.
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