React useComponentWillUnmount Hook

Introduction

In this lab, we will explore the useComponentWillUnmount hook in React, which allows us to execute a callback function right before a component is unmounted and destroyed. By using this hook, we can perform any necessary cleanup tasks, such as removing event listeners or cancelling any pending requests. This lab will provide hands-on experience in using this hook and understanding its behavior, which is similar to the componentWillUnmount() lifecycle method in class components.

React useComponentWillUnmount Hook

index.html and script.js have already been provided in the VM. In general, you only need to add code to script.js and style.css.

To execute a callback immediately before a component is unmounted and destroyed, you can use the useEffect() hook with an empty array as the second argument. Return the provided callback to be executed only once before cleanup. This behavior is similar to the componentWillUnmount() lifecycle method of class components. You can also use the following code snippet to create a custom hook useComponentWillUnmount() that takes an onUnmountHandler function as an argument and executes it before the component is unmounted:

const useComponentWillUnmount = (onUnmountHandler) => {
  React.useEffect(
    () => () => {
      onUnmountHandler();
    },
    []
  );
};

You can then use this custom hook in your functional component like this:

const Unmounter = () => {
  useComponentWillUnmount(() => console.log("Component will unmount"));

  return <div>Check the console!</div>;
};

ReactDOM.createRoot(document.getElementById("root")).render(<Unmounter />);

This will log "Component will unmount" to the console when the component is about to be unmounted.

Please click on 'Go Live' in the bottom right corner to run the web service on port 8080. Then, you can refresh the Web 8080 Tab to preview the web page.

Summary

Congratulations! You have completed the React useComponentWillUnmount Hook lab. You can practice more labs in LabEx to improve your skills.