React is a JavaScript library for building user interfaces. So if you are using ReactJS, then you must go through these interview questions to prepare for a higher role in in Web development.

Q.1 What do you know about JSX in React and its importance in React
JSX is a XML-like syntax extension to Javascript and expands to JavaScript XML. JSX produces React “elements”. JSX is a preprocessor step that adds XML syntax to JavaScript. We can use React without JSX but JSX makes React a lot more elegant. Just like XML, JSX tags have a tag name, attributes, and children. The first part of a JSX tag determines the type of the React element. After compilation, JSX expressions become regular JavaScript objects.
Q.2 What is meant by Virtual DOM in React and its relevance
Virtual DOM is an object, which is a representation of DOM object with same properties as a real DOM object. It is lightweight and detached from the browser-specific implementation details. It does not change directly what’s on the screen. Manipulating the virtual DOM is faster as compared to DOM, as nothing gets drawn on screen. To explain, changing virtual DOM is similar to editing a blueprint, against moving rooms in an actual house.
Q.3 How does React works, to accomplish frontend customer facing services for a web application
React makes a virtual DOM tree-like structure similar to DOM with elements as specified. When there is a state change in a component, first it runs a “diffing” algorithm, to locate what has changed in the virtual DOM. Then reconciliation is done which updates the DOM with the results of diff.
Q.4 What is meant by Component in React
Components forms the core of React and is the building blocks of React app. Component is a JavaScript class or function which may accept inputs or properties(props) and returns a React element that describes how a part of the UI (User Interface) should appear.
Q.5 How to create Component in React
Component in React can be created as Function Component, which is JavaScript functions that accept props object as first parameter and return React elements or as, Class Component, which requires extending React.Component and creating a render function which returns a React element.
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