Unhandled Runtime Error in Next.js: Causes and How to Fix

Check the Error Output

• Examine the detailed error message in the terminal or browser's console. This information often highlights where the error originated and provides a stack trace to help trace back to the source.

 

• Note any specific line numbers or components mentioned. This can significantly streamline the debugging process.

Identify the Component or Function Causing the Error

• Locate the component or function mentioned in the error output. Carefully review it for incorrect logic or potential runtime issues.

 

• Common issues include accessing undefined variables, faulty asynchronous logic, or outdated lifecycle methods. Ensure that all props and states are correctly used and initialized.

Utilize Error Boundaries

• Implement error boundaries in your application to catch errors in React components. Error boundaries can catch errors in render lifecycles and display fallback UIs instead.

class ErrorBoundary extends React.Component {
    constructor(props) {
        super(props);
        this.state = { hasError: false };
    }

    static getDerivedStateFromError(error) {
        return { hasError: true };
    }

    render() {
        if (this.state.hasError) {
            return <h1>Something went wrong.</h1>;
        }

        return this.props.children; 
    }
}

Use Try/Catch Blocks

• Wrap potentially faulty function calls within a try/catch block to handle exceptions gracefully. This is particularly useful for promises and async/await expressions.

try {
    const result = await fetchData();
    // Process result
} catch (error) {
    console.error("An error occurred:", error);
}

Check for Asynchronous Issues

• Ensure that asynchronous operations have proper error handling. This includes checking that promises are resolved or rejected properly and all async logic functions have appropriate try/catch blocks.

Validate Environment Variables

• Verify that all environment variables required by your application are correctly set and available. Missing or incorrect environment configurations can lead to runtime errors.

 

• Use process.env to access these variables and ensure your .env.local or similar configuration files are properly set up if necessary.

Update Dependencies

• Outdated dependencies can sometimes lead to unhandled runtime errors due to incompatibilities. Ensure that your project's dependencies are up to date.

npm update

Inspect Third-Party Libraries

• If the issue appears to originate from a third-party library, check the library's repository for open issues or potential patches. Switch to actively maintained alternatives if necessary.

Debugging and Logs

• Incorporate more logging to track variables and application flow. Strategically placed log statements can help isolate where the error arises within your application logic.

 

• Use console.log() or more advanced logging solutions depending on your project's needs.

console.log("Debug value of variable:", myVariable);