In a React class component, the mounting phase refers to the initial creation and rendering of the component, from its instantiation to its insertion into the DOM. During the mounting phase, several lifecycle methods are called in a specific order:
constructor(props): This is the first method called when an instance of the component is created. It’s used to initialize state and bind event handlers.
static getDerivedStateFromProps(props, state): This static method is invoked right before rendering and is used to compute and return a new state object based on the updated props. It’s rarely used in favor of
componentDidUpdateor using controlled components.
render(): This method is responsible for rendering the component’s JSX markup. It should be a pure function that only returns the JSX representation of the component. It should not modify the component state or interact with the DOM directly.
componentDidMount(): This method is called immediately after the component is inserted into the DOM. It’s commonly used to initialize third-party libraries, perform API requests, or set up event listeners. Any asynchronous operations initiated here should be cleaned up in the
During the mounting phase, these methods are called in the given order. Once the mounting phase is completed, the component is considered “mounted” and is ready for user interaction or further updates.
It’s important to note that with the introduction of React Hooks in React 16.8, functional components and the
useEffect hook provide an alternative and more flexible way to handle component lifecycle and side effects, including the mounting phase.