The updating phase of the React component lifecycle occurs when the component's state or props are changed. During this phase, several methods are executed to update the component and re-render it with the new data.

Here are the methods involved in the updating phase:

• static getDerivedStateFromProps(): This static method is called after the component is created and before it is re-rendered. It receives the updated props and the current state as parameters and allows you to update the state based on the new props. It should return an object to update the state, or null to indicate no changes are necessary.

• shouldComponentUpdate(): This method is called before the rendering phase to determine if the component should re-render or not. By default, it returns true, indicating that the component should re-render. However, you can implement custom logic in this method to optimize rendering by avoiding unnecessary re-renders. For example, if the new props or state are the same as the previous ones, you can return false to skip the re-rendering process.

• render(): The render method is called to generate the updated JSX markup for the component. It should be a pure function, meaning it should not modify the component's state or interact with the DOM directly.

• getSnapshotBeforeUpdate(): This method is called right before the updated component is committed to the DOM. It allows you to capture some information from the DOM before it is potentially changed. The value returned from this method will be passed as a parameter to the componentDidUpdate method.

• componentDidUpdate(): This method is called after the component is updated and the changes are flushed to the DOM. It receives the previous props, previous state, and the value returned from getSnapshotBeforeUpdate() as parameters. This method is commonly used to perform side-effects after an update, such as fetching new data based on the updated props or interacting with external libraries.

Let's take a look at an example that demonstrates the updating phase methods:

1// Example of the updating phase methods in a component
2
3class MyComponent extends React.Component {
4  constructor() {
5    super();
6    // Initialize state
7    this.state = {
8      count: 0
9    };
10  }
11
12  static getDerivedStateFromProps(nextProps, prevState) {
13    // Update state based on props
14    if (nextProps.value !== prevState.value) {
15      return {
16        count: nextProps.value
17      };
18    }
19
20    return null;
21  }
22
23  shouldComponentUpdate(nextProps, nextState) {
24    // Don't re-render if the count is the same
25    return nextState.count !== this.state.count;
26  }
27
28  render() {
29    return (
30      <div>
31        <h1>Count: {this.state.count}</h1>
32      </div>
33    );
34  }
35
36  getSnapshotBeforeUpdate(prevProps, prevState) {
37    // Capture the current scroll position
38    return window.scrollY;
39  }
40
41  componentDidUpdate(prevProps, prevState, snapshot) {
42    // Scroll to the captured position
43    window.scrollTo(0, snapshot);
44  }
45}

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``js

// replace with ts logic relevant to content

// make sure to log something

for (let i = 1; i <= 100; i++) {

  if (i % 3 === 0 && i % 5 === 0) {

      console.log("FizzBuzz");

  } else if (i % 3 === 0) {

      console.log("Fizz");

  } else if (i % 5 === 0) {

      console.log("Buzz");

  } else {

      console.log(i);

  }

}

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Let's continue on the next screen!

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