Error Boundaries

What Are Error Boundaries?

Error boundaries are special React components that catch JavaScript errors during rendering, in lifecycle methods, and in constructors of components below them in the component tree. Instead of causing the entire application to crash, error boundaries log the errors and render a fallback UI.

Why Use Error Boundaries?

1. Prevent Full Application Crashes

Without error boundaries, an error in one component can cause the entire application to break. Error boundaries allow graceful degradation by catching errors and displaying an alternative UI.

2. Isolate Errors to Specific Components

Error boundaries confine errors to the component subtree where they occur, preventing them from affecting unrelated parts of the application.

3. Log Errors for Debugging

They provide a structured way to log errors (e.g., sending them to an external logging service like Sentry or LogRocket) to help diagnose and fix issues.

When Not to Use Error Boundaries

• Event Handlers: Error boundaries do not catch errors inside event handlers. You need to use try-catch within event handlers.
• Asynchronous Code: Promises and async functions are not caught by error boundaries. Use .catch() for handling promise rejections.
• Server-Side Rendering (SSR): Error boundaries do not catch errors during SSR since they only work in the browser.

Implementing an Error Boundary

Error boundaries are class components that use the lifecycle methods static getDerivedStateFromError and componentDidCatch to catch and handle errors.

Example: Error Boundary Components

import React from "react";
 
class ErrorBoundary extends React.Component {
  constructor(props) {
    super(props);
    this.state = { hasError: false };
  }
 
  static getDerivedStateFromError(error) {
    // Update state so the next render shows the fallback UI
    return { hasError: true };
  }
 
  componentDidCatch(error, info) {
    console.error("Error caught by Error Boundary:", error, info);
    // You can log the error to an external service here
  }
 
  render() {
    if (this.state.hasError) {
      return <h2>Something went wrong. Please try again later.</h2>;
    }
    
    return this.props.children;
  }
}
 
export default ErrorBoundary;

Wrap your components inside the ErrorBoundary to catch errors and prevent crashes.

import ErrorBoundary from "./ErrorBoundary";
import MyComponent from "./MyComponent";
 
function App() {
  return (
    <ErrorBoundary>
      <MyComponent />
    </ErrorBoundary>
  );
}

Best Practices

• Wrap high-risk components (e.g., third-party components, dynamic UI elements) with an error boundary.
• Log errors to an external service for monitoring and debugging.
• Provide a meaningful fallback UI to improve user experience.

By implementing error boundaries, you can build more resilient and user-friendly React applications.