React useError Hook

Introduction

In this lab, we will learn how to create an error dispatcher using the useError hook in React. The hook allows us to create a state variable that holds an error and throw it whenever it's truthy. We will also use the useCallback hook to update the state and return the cached function. By the end of this lab, you will be able to effectively handle errors in your React applications.

Skills Graph

React useError 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.

This code creates an error dispatcher. It uses three React hooks to manage the error state and dispatch it to the user interface.

Here's how the code works:

1. The useState() hook creates a state variable called error that holds the error object. It takes an initial value of err, which is passed in as an argument to the hook.

2. The useEffect() hook is used to "throw" the error whenever it's truthy. This hook takes a function and an array of dependencies as arguments. In this case, the function checks if the error state variable is truthy (i.e. not null, undefined, 0, false, or an empty string), and throws it if it is. The array of dependencies is [error], which means the effect will be re-run whenever the error variable changes.

3. The useCallback() hook is used to create a cached function called dispatchError, which updates the error state variable and returns the new function. This hook takes a function and an array of dependencies as arguments. In this case, the function takes an argument err, which is the new error object to be dispatched. The array of dependencies is [], which means the cached function will only be re-created if the component is re-rendered.

Here's an example of how to use the useError() hook in a component:

1. Create a new component called ErrorButton.

2. Inside the component, call the useError() hook to get the dispatchError function.

3. Create a click handler function called clickHandler that calls dispatchError with a new error object.

4. Render a button that calls clickHandler when clicked.

Here's the code:

const useError = (err = null) => {
  const [error, setError] = React.useState(err);

  React.useEffect(() => {
    if (error) {
      throw error;
    }
  }, [error]);

  const dispatchError = React.useCallback((err) => {
    setError(err);
  }, []);

  return dispatchError;
};

const ErrorButton = () => {
  const dispatchError = useError();

  const clickHandler = () => {
    dispatchError(new Error("Error!"));
  };

  return <button onClick={clickHandler}>Throw error</button>;
};

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

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 useError Hook lab. You can practice more labs in LabEx to improve your skills.