React developer interview questions

The React course will teach you how to make your own apps for usage on your phone, computer, or anywhere else. Frequently asked react js interview questions may be found in this page.

1.What is the purpose of a Router in React?

ANS:React Router is essential for displaying different views in a single page application. It is used in the app to define numerous routes. When a user enters a certain URL into the browser, if the URL path matches any 'route' inside the router file, the user will be routed to that Route. So, we need to add a Router module to the React project, which allows us to create many routes, each of which leads to a different view.

2.What exactly is React Router?

ANS:React Router is a general-purpose routing framework system developed on top of React. It is used to implement routing in a React application by utilising the React Router Package. It assists you in defining numerous paths in the app. It populates the browser's synchronous URL with data that will be shown on the web page. It preserves the application's standard structure and behaviour and is primarily used for developing single-page web applications.

3.What is the purpose of references?

ANS:In React, the Ref is used in the following situations: It is used to return the element's reference. It is used when DOM measurements are required, such as when controlling focus, text selection, or media playback. It is used to initiate urgent animations. When interacting with third-party DOM libraries, it is utilised. It can also be used as a callback.

4.Which is preferable, callback references or findDOMNode()?

ANS:The preferable method is to utilise callback references instead of the findDOMNode() API. Because callback refs provide more control over when refs are set and unset, whereas findDOMNode() inhibits future React advancements.

5.What exactly are Forward Refs?

ANS:Ref forwarding is a feature that allows a ref to be passed from one component to one of its child components. It is possible to accomplish this by using the React.forwardRef() function. It is very handy with higher-order components and is commonly used in reusable component libraries.

6.How do I make a ref?

ANS:React may be used to build refs. createRef() and then connected to React components using the ref property. When a component is built, it is often assigned to an instance property and may then be referenced throughout the component.

7.What do you mean when you say "refs" in React?

ANS:In React, references are referred to as refs. It is a property that allows you to save a reference to certain DOM nodes or React components. It demonstrates how to access React DOM nodes or React elements and interact with them. It's utilised when we don't want to use props to modify the value of a child component.

8.What exactly do you mean by props in React?

ANS:Props are inputs to components in React. They are either single values or objects that include a group of values that are supplied to components when they are created using a naming scheme similar to HTML-tag attributes. They are bits of information transferred from a parent component to a child component.

9.What do you mean by the term "state" in React?

ANS:In react, a component's state is an object that contains information that may change during the component's lifespan. It is best to keep your state as basic as possible and to keep the number of stateful components to a minimum.

10.Is it feasible for a web browser to natively read JSX?

ANS:JSX cannot be read directly by web browsers. This is because web browsers are only designed to read standard JS objects, and JSX is not a typical JavaScript object. If you want a web browser to read a JSX file, you must first convert it to a standard JavaScript object. Babel is used for this reason.

11.When should we utilise a class component instead of a function component?

ANS:If a component requires state or lifecycle methods, the class component should be used; otherwise, the function component should be used. However, with the advent of Hooks in React 16.8, you could access state, lifecycle methods, and other capabilities that were previously exclusively available in the class component directly in your function component.

12.What exactly is create-react-app?

ANS:Create React App is a Facebook tool for creating React apps. It allows you to build single-page React apps. The preset create-react-app spares you from time-consuming setup and configuration like Webpack or Babel.

13.In React, how do you add validation to props?

ANS:Props validation is a tool that assists developers in avoiding future faults and issues. It improves the readability of your code. Although it is not required to design components using propTypes, React components employ a specific property called PropTypes that helps you identify errors by checking the data types of values supplied through props. In the React component, we may validate props by using App.propTypes. When some of the props are given with an incorrect type, the JavaScript console will display warnings. You must set the App.defaultProps after setting the validation rules.

14.Why are fragments preferable to container divs?

ANS:Fragments are quicker and use less memory since they do not construct an additional DOM node. Some CSS styles, such as CSS Grid and Flexbox, have a special parent-child connection and add div> tags in the middle, making it difficult to maintain the desired layout. The DOM Inspector has been less crowded.

15.What exactly are fragments?

ANS:It was first introduced in the React 16.2 version. Fragments are used in React for components that return several items. It enables you to group a list of several children without adding an additional node to the DOM.

16.Why do component names have to begin with a capital letter?

ANS:In React, component names must begin with a capital letter. If we begin the component name with lower case, an error like an unknown tag will be thrown. It's because lower case tag names are treated as HTML tags in JSX.

17.What may HOC be used for?

ANS:HOC can perform a variety of jobs, some of which are listed below: Reusability of Code Manipulating props State tampering

18.Higher Order Components (HOC) are what they sound like.

ANS:Higher Order Component is an advanced way for reusing component code in React. It's a function that accepts a component and returns a new one. To put it another way, it is a function that takes another function as an argument. According to the official website, it is not a feature (component) of the React API, but rather a pattern that emerges from the compositional structure of React.

19.What exactly are Pure Components?

ANS:Pure components were introduced in the 15.3 version of React. The components React.Component and React. The shouldComponentUpdate() React lifecycle function distinguishes PureComponent. This method determines if the component should be re-rendered by returning a boolean value (true or false). By default, the shouldComponentUpdate() function in React.Component returns true. React.PureComponent, on the other hand, examines changes in state or props to re-render the component. The pure component improves the code's simplicity and the application's efficiency.

20.In React, how are forms created?

ANS:Forms allow users to engage with the programme while also gathering information from them. Forms may conduct a variety of activities such as user authentication, user addition, searching, filtering, and so on. Text fields, buttons, checkboxes, radio buttons, and other controls can be found on a form. React provides a stateful, reactive approach to form development. React forms are comparable to HTML forms. However, with React, the state property of the component is only modified using setState(), and their submission is handled by a JavaScript function. This function has complete access to the data that the user enters into a form.

If you're a frontend developer looking to master the basics of React.js, A2N Academy is the place to go. From the ground up, the Reactjs course will teach you the fundamentals and prepare you for the job market.