error-handling.md

description
Handle errors in your Next.js app.

Error Handling

This documentation explains how you can handle development, server-side, and client-side errors.

Handling Errors in Development

When there is a runtime error during the development phase of your Next.js application, you will encounter an overlay. Fixing the error will automatically dismiss the overlay. It is only visible when the development server runs using next dev, npm run dev, or yarn dev and not in production.

Handling Server Errors

Next.js provides a static 500 page by default to handle server-side errors that occur in your application. This page generates at build time. You can also customize this page by creating a pages/500.js file.

Having a 500 page in your application does not show specific errors to the app user.

Handling Client Errors

React Error Boundaries is a graceful way to handle a JavaScript error on the client so that the other parts of the application continue working. In addition, it prevents crashing the whole application's page, and you can display a fallback UI component.

To use Error Boundaries for your Next.js application, you must create a class component ErrorBoundary and wrap the Component prop in the pages/_app.js file. This component will be responsible to:

• Render a fallback UI after an error is thrown
• Provide a way to reset the Application's state
• Log error information

Using a class component from React library, you can create an ErrorBoundary component. Here is an example:

class ErrorBoundary extends React.Component {
  constructor(props) {
    super(props)

    // Define a state variable to track whether is an error or not
    this.state = { hasError: false }
  }
  static getDerivedStateFromError(error) {
    // Update state so the next render will show the fallback UI

    return { hasError: true }
  }
  componentDidCatch(error, errorInfo) {
    // You can use your own error logging service here
    console.log({ error, errorInfo })
  }
  render() {
    // Check if the error is thrown
    if (this.state.hasError) {
      // You can render any custom fallback UI
      return (
        <div>
          <h2>Oops, there is an error!</h2>
          <button
            type="button"
            onClick={() => this.setState({ hasError: false })}
          >
            Try again?
          </button>
        </div>
      )
    }

    // Return children components in case of no error

    return this.props.children
  }
}

export default ErrorBoundary

The ErrorBoundary component keeps track of an hasError state. The value of this state variable is a boolean. When the value of hasError is true, then the ErrorBoundary component will render a fallback UI. Otherwise, it will render the children components.

After creating an ErrorBoundary component, import it in the pages/_app.js file to wrap the Component prop in your Next.js application.

// Import the ErrorBoundary component
import ErrorBoundary from '../components/ErrorBoundary'

function MyApp({ Component, pageProps }) {
  return (
    // Wrap the Component prop with ErrorBoundary component
    <ErrorBoundary FallbackComponent={ErrorFallback}>
      <Component {...pageProps} />
    </ErrorBoundary>
  )
}

export default MyApp

You can learn more about Error Boundaries in React's documentation.

Reporting Errors

To monitor client errors, use a service like Sentry, Bugsnag or Datadog.