Cannot read property 'pathname' of undefined in Next.js: Causes and How to Fix

Identify the Source of the Error

• Check your component or hook where you're trying to access pathname. Ensure that you're not accessing it from an undefined object.

 

• Look at how you're importing useRouter from next/router. Make sure it is imported and used correctly in your component.

Ensure Proper Usage of useRouter

• In a React component, make sure to use useRouter correctly. A typical implementation looks like this:

 

import { useRouter } from 'next/router';

const MyComponent = () => {
  const router = useRouter();

  // Use router.pathname safely
  console.log(router.pathname);

  return <div>Check the console for pathname</div>;
};

 

• If using functional components, ensure useRouter is called within a component's body, not inside a conditional block or a loop.

Checking Server-Side Code

• When making server-side calls, ensure you check the request object. Access pathname from the server-side context properly:

 

// Example in getServerSideProps
export async function getServerSideProps({ req }) {
  console.log(req.url); // Verifies the received URL
  return { props: {} };
}

 

• Utilize server-side props functions like getServerSideProps or getStaticProps appropriately when accessing request properties.

Refactor Conditional Logic

• If the error arises within a conditional block, make sure to safely access pathname by adding condition checks:

 

const SafeComponent = () => {
  const router = useRouter();

  if (router && router.pathname) {
    console.log(router.pathname);
  } else {
    console.log('Pathname is undefined');
  }

  return <div>Check the console for pathname</div>;
};

 

• Ensure all objects from which pathname can be accessed are properly defined and initialized.

Using Context or Global State

• If building complex applications, consider using context or a global state for routing details to avoid redundant access by various components.

 

• Example of using React Context for routing information:

 

import { createContext, useContext } from 'react';
import { useRouter } from 'next/router';

const PathnameContext = createContext();

export const PathnameProvider = ({ children }) => {
  const { pathname } = useRouter();
  
  return (
    <PathnameContext.Provider value={pathname}>
      {children}
    </PathnameContext.Provider>
  );
};

export const usePathname = () => useContext(PathnameContext);

 

• Wrap your application or specific components with PathnameProvider to provide easy access to pathname.

Debugging with Logs and Error Boundaries

• Utilize console logs and error boundaries to identify where your code might be failing:

 

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

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

  componentDidCatch(error, errorInfo) {
    console.log(error, errorInfo);
  }

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

    return this.props.children;
  }
}

// Wrap your component
<ErrorBoundary>
  <MyComponent />
</ErrorBoundary>

 

• Implement error handling to capture details whenever property access might lead to undefined errors.