React Component Life Cycle

In React, a component's life cycle refers to the different stages a component goes through from when it is first created until it is unmounted (removed) from the DOM. The life cycle of a component can be divided into three main phases:

  1. Mounting: This is the phase where a component is being added to the DOM. During the mounting phase, the following lifecycle methods are called in the following order:
  • constructor: This method is called before the component is mounted. It is used to set up the initial state of the component and to bind the component's methods to the correct context.
  • getDerivedStateFromProps: This method is called before the render method and is used to update the component's state based on the props.
  • render: This method is called to render the JSX for the component.
  • componentDidMount: This method is called after the component is mounted and the JSX has been rendered to the DOM. It is a good place to put code that needs to be executed after the component has been rendered, such as making API calls or setting up event listeners.
  1. Updating: This is the phase where a component is being re-rendered due to changes in its props or state. During the updating phase, the following lifecycle methods are called in the following order:
  • getDerivedStateFromProps: This method is called before the render method and is used to update the component's state based on the props.
  • shouldComponentUpdate: This method is called before the render method and is used to determine whether the component should be re-rendered or not. It is a good place to put optimization logic to prevent unnecessary re-renders.
  • render: This method is called to render the JSX for the component.
  • getSnapshotBeforeUpdate: This method is called just before the DOM is updated and is used to capture a snapshot of the DOM before the updates are made.
  • componentDidUpdate: This method is called after the component has been updated and the DOM has been updated. It is a good place to put code that needs to be executed after the component has been updated, such as making API calls or updating event listeners.
  1. Unmounting: This is the phase where a component is being removed from the DOM. During the unmounting phase, the following lifecycle method is called:
  • componentWillUnmount: This method is called just before the component is unmounted and is a good place to put code that needs to be executed before the component is removed, such as cleaning up

Here are a few more things you might want to know about the component life cycle in React:

  • The component life cycle methods are only available in class-based components. If you are using functional components, you can use the useEffect Hook to perform side effects such as making API calls or setting up event listeners. The useEffect Hook is called after the component is rendered and can be used to perform side effects in a way that is similar to the componentDidMount, componentDidUpdate, and componentWillUnmount lifecycle methods.

  • You can control the order in which the lifecycle methods are called by using the React.Suspense component. The React.Suspense component allows you to suspend the rendering of a component until certain conditions are met, such as data being fetched from an API. When a component is suspended, the rendering of the component is paused and the componentWillUnmount method is not called until the component is resumed. This can be useful for optimizing the performance of your application by avoiding unnecessary unmounting and remounting of components.

  • You can use the React.memo higher-order component to optimize the performance of your functional components. The React.memo higher-order component is similar to the shouldComponentUpdate lifecycle method in class-based components, in that it allows you to control whether a functional component should be re-rendered or not. The React.memo higher-order component will only re-render the component if the props have changed, which can help improve the performance of your application by avoiding unnecessary re-renders.