Lifecycle methods in React

 A component in React has three phases of lifecycle:

        1. Mounting Phase

                Mounting means adding elements into the DOM.

                React provides some build in methods which are called when elements are mounted into the DOM and there methods are:

• constructor(): in class Component, it is called before anything else. Hence it is used to set up the initial state of the component.
• componentDidMount(): It is called when a component is rendered

        2. Updation Phase

                This is next phase after mounting. It is used to keep track of changes in a component.

                A class or functional component updates itself whenever any change occurs in state or props value. React provides the following methods to call, when a component is updated:

• shouldComponentUpdate(): returns a boolean value that specifies whether React shold continue rendering or not.
• componentDidUpdate(): called after the component is updated in the DOM.

                
        3. Unmounting Phase

                This is the last phase. When a component is removed from the DOM, called unmounting.

                React provides the following method to handle unmounting of component:

• componentWillUnmount(): called when the component is about to be removed from the DOM.

Continue Learning: React Hooks