Answer:- The important React lifecycle methods are: - getInitialState(): It is used to specify the default value of this.state. It is executed before the creation of the component. - componentWillMount(): It is executed before a component gets rendered into the DOM. - componentDidMount(): It is executed when the component gets rendered and placed on the DOM. Now, you can do any DOM querying operations. - componentWillReceiveProps(): It is invoked when a component receives new props from the parent class and before another render is called. If you want to update the State in response to prop changes, you should compare this.props and nextProps to perform State transition by using this.setState() method. - shouldComponentUpdate(): It is invoked when a component decides any changes/updation to the DOM and returns true or false value based on certain conditions. If this method returns true, the component will update. Otherwise, the component will skip the updating. - componentWillUpdate(): It is invoked before rendering takes place in the DOM. Here, you cant change the component State by invoking this.setState() method. It will not be called, if shouldComponentUpdate() returns false. - componentDidUpdate(): It is invoked immediately after rendering takes place. In this method, you can put any code inside this which you want to execute once the updating occurs. - componentWillUnmount(): It is invoked immediately before a component is destroyed and unmounted permanently. It is used to clear up the memory spaces such as invalidating timers, event listener, canceling network requests, or cleaning up DOM elements. If a component instance is unmounted, you cannot mount it again.

Answer:- Pure components introduced in React 15.3 version. The React.Component and React.PureComponent differ in the shouldComponentUpdate() React lifecycle method. This method decides the re-rendering of the component by returning a boolean value (true or false). In React.Component, shouldComponentUpdate() method returns true by default. But in React.PureComponent, it compares the changes in state or props to re-render the component. The pure component enhances the simplicity of the code and performance of the application.

Answer:- In React, Higher Order Component is an advanced technique for reusing component logic. It is a function that takes a component and returns a new component. In other words, it is a function which accepts another function as an argument. According to the official website, it is not the feature(part) in React API, but a pattern that emerges from Reacts compositional nature.

Answer:- You can do many tasks with HOC, some of them are given below: - Code Reusability - Props manipulation - State manipulation - Render highjacking

Answer:- In React, it is necessary to start component names with a capital letter. If we start the component name with lower case, it will throw an error as an unrecognized tag. It is because, in JSX, lower case tag names are considered as HTML tags.

Answer:- In was introduced in React 16.2 version. In React, Fragments are used for components to return multiple elements. It allows you to group a list of multiple children without adding an extra node to the DOM.

Answer:- - Fragments are faster and consume less memory because it did not create an extra DOM node. - Some CSS styling like CSS Grid and Flexbox have a special parent-child relationship and add