Top 10 React Questions and Answers for Interview Preparation

React is a declarative, competent and supple JavaScript library to build user interfaces. It will let the developer compose UIs from small and isolated pieces of code which are known as components. It is one of the popular front-end libraries which have been used by Facebook and so many other big companies. Here are the top 10 React Interview Question and Answers Book which are mainly asked by the interviewer. 

1#. What is React?

React is a front-end JavaScript library which has been developed by Facebook in the year 2011. It mainly follows the component-based approach to building reusable UI components. React is used to develop interactive and complex web and mobile UI.

2#. Mention some of the major advantages of React.

Find below some of the major advantages of React:

• React increases the performance of the application.
• It can be conveniently used on the client and server-side both as well. 
• Not only that, React JSX can increase the readability of the code and writing UI test cases by using React is really easy. 
• React is also easy to integrate with so many other frameworks like Angular, Meteor etc.
• Lots of major companies are now working on React JS to fulfil their work in a smoothly way and thus the demand of React JS certified and experienced person are increasing day by day and doing React JS Online course has become so essential to cope up with this.
  
  

3#. What is JSX?

The full form of JSX is JavaScript XML. This is a type of file used by React to utilize the expressiveness of JavaScript along with HTML like template syntax. This will ultimately make the HTML file really easy to understand. Such type of file makes the applications robust and boosts their performance. 

4#. Tell us some features of React JS?

Some of the features of React are:

• It uses server-side rendering.
• React uses the virtual DOM rather than the real DOM.
• It also follows unidirectional data binding or data flow.
  
  

5#. What is Virtual DOM?

Virtual DOM is a lightweight JavaScript object that is just a copy of the real DOM. It is a node tree that can list the elements, contents as objects and also their attributes and properties. The render function of React creates a node tree with the components of the React. After that, it will update the tree in response to the mutations of the data model that is caused by various activities done by the users or maybe by the systems. Virtual DOM simple works on three different steps:

• When any fundamental data changes, the complete UI is re-rendered in virtual DOM representation. 
• The difference between the prior DOM representation and the new one is then calculated.
• Once the calculations are done, the real DOM will be updated with the things which have actually changed.

6#. Describe some limitations of React?

• React is just a library. It is not a full brown framework.
• It can be difficult for the new programmers to understand it easily.
• The library of React is very large and would take time to understand.
• Coding gets complex as it uses JSX and an inline template.
  
  

7#. What is State in React and how it can be used?

States are the source of data that needs to be kept as simple as possible. States are the objects which decide components behaviour and depiction. They can create dynamic and interactive components and can be accessed through this. state().

8#. What is Props?

Properties in React are termed as Props. It is a read-0only component that can be kept immutable. Props are mainly passed down from the parent to the child components throughout the application. However, the child component is not able to send the Prop back to the parent component. It will ultimately help to maintain the unidirectional data flows that are used to render the dynamically generated data. 

9#. What is the purpose of using render () in React?

Each React component must use the render () as it returns a single React element which is mainly the representation of the native DOM component. Now, if more than one HTML elements requires to be rendered, then they will group together inside one enclosing tag like <form>, <div>, <group> etc. This function will return the same result each time it is invoked. 

10#. What are the Synthetic events in React?

Synthetic events are the objects which work as a cross-ware wrapper around the browser’s native event. They will combine the behaviour of different browsers into one API. This is done so that the events show consistent properties across various browsers. 

 Hope the above Interview Questions will help you to look forward to the interview preparation. However, studying an interview questions and answers book or pdf file will able to make you prepared for the interview with their huge collections of interview questions and answers. 

If you want to know more details and want to develop your interest in React, then taking React JS training online from a trusted organization is very much necessary.