What is “Mounting” in React.js?

React.js is a popular JavaScript library used for building user interfaces. One of the key concepts in React.js is “Mounting,” which refers to the process of creating a React component and inserting it into the DOM (Document Object Model).

Mounting is divided into three phases: componentWillMount, render, and componentDidMount. Let’s take a closer look at each of these phases and their purpose.

1. componentWillMount

The componentWillMount phase is executed just before the component is rendered. It is commonly used for initializing state, making API calls, or setting up subscriptions. However, it is important to note that this phase is considered legacy and may be deprecated in future versions of React.

Here’s an example of how to use componentWillMount:

{`class MyComponent extends React.Component {
  componentWillMount() {
    // Initialize state or make API calls
  }
  
  render() {
    // Render component
  }
  
  componentDidMount() {
    // Perform any necessary cleanup or additional setup
  }
}`}

2. render

The render phase is responsible for generating the HTML markup for the component. It is a pure function that should not modify component state or interact with the DOM directly. The render method must return a single React element or null.

Here’s an example of the render method:

{`class MyComponent extends React.Component {
  render() {
    return (
      

        
Hello, World!
      
    );
  }
}`}

3. componentDidMount

The componentDidMount phase is executed immediately after the component has been inserted into the DOM. It is commonly used for performing side effects, such as fetching data from an API or subscribing to events. This phase is a good place to interact with the DOM or initialize third-party libraries.

Here’s an example of how to use componentDidMount:

{`class MyComponent extends React.Component {
  componentDidMount() {
    // Perform side effects or interact with the DOM
  }
}`}

By understanding the mounting process in React.js, you can effectively manage component initialization and interact with the DOM at the appropriate times. Remember to use componentWillMount for any necessary setup, render for generating the component’s markup, and componentDidMount for any post-render operations.

Happy mounting!