How to Use the React getSnapshotBeforeUpdate() Method

09/28/2021

Contents

In this article, you will learn how to use the React getSnapshotBeforeUpdate() method.

Using the getSnapshotBeforeUpdate() method

The getSnapshotBeforeUpdate() method is a lifecycle method in React that allows you to capture a snapshot of the current state of your component before it gets updated. This method is invoked immediately before the most recent render is committed to the screen, and can be useful for saving information about the component’s current state that might be lost during the update.

Here are the steps to use the getSnapshotBeforeUpdate() method in your React component:

Define the method in your component class:

class MyComponent extends React.Component {
  constructor(props) {
    super(props);
    this.state = { count: 0 };
  }

  getSnapshotBeforeUpdate(prevProps, prevState) {
    // Code to capture snapshot
  }

  // Other methods and render function here...
}

Implement the method to capture the snapshot of the current state: The getSnapshotBeforeUpdate() method takes two parameters: prevProps and prevState, which are the props and state values before the component updated. You can use these parameters to compare the previous and current state of the component and capture any changes you want to preserve. The method should return a value that will be passed to the componentDidUpdate() method.

getSnapshotBeforeUpdate(prevProps, prevState) {
  if (prevState.count !== this.state.count) {
    return { count: this.state.count };
  }
  return null;
}

Use the snapshot value in the componentDidUpdate() method: The value returned by getSnapshotBeforeUpdate() will be passed as the third parameter to the componentDidUpdate() method, which is invoked after the component has been updated with new props and state values. You can use the snapshot to perform any necessary actions, such as updating the DOM or saving state to local storage.

componentDidUpdate(prevProps, prevState, snapshot) {
  if (snapshot !== null) {
    console.log('Count changed from', prevState.count, 'to', this.state.count);
  }
}
#React