Why Do I Get Fetch Errors During My Next.js Static Website Production Build?

Fetch Error During Next.js Static Website Production Build

When building a Next.js website in production, you may encounter fetch errors that do not occur when running in development mode. This can be frustrating and confusing.

Understanding the Error

The error message "FetchError: invalid json response body at ..." often indicates a problem with the JSON response returned by your API route. Specifically, the error "Unexpected token T in JSON at position 0" suggests that the server is returning invalid JSON data.

Causes and Solutions

Calling Internal API Routes

In Next.js, it's essential to avoid calling internal API routes inside getStaticProps. Internal API routes are not available during build-time because the server has not yet been started.

Solution: Replace the API route call in getStaticProps with direct server-side code that performs the necessary data fetching.

Absolute URLs in fetch

If you remove the assetPrefix from next.config.js, ensure that the URLs used in fetch are absolute. Relative URLs may not work in production builds.

Solution: Modify the fetch calls to use absolute URLs.

Code Refactor

Here is a refactored version of your code that avoids the errors:

// pages/product/[slug]
import db from '../../../data/products'

// Remaining code...

export const getStaticProps = async ({ params: { slug }, locale }) => {
  const result = db.filter(item => item.slug === slug);
  const data = result.filter(item => item.locale === locale)[0];
  const { title, keywords, description } = data;
  return {
    props: {
      data,
      description,
      keywords,
      title,
    },
  };
};

export const getStaticPaths = async () => {
  const paths = db.map(({ slug, locale }) => ({ params: { slug }, locale }));
  return {
    fallback: true,
    paths,
  };
};

Conclusion

By understanding the causes of fetch errors during Next.js production builds and applying the appropriate solutions, you can ensure a successful deployment of your static website. Remember to avoid calling internal API routes in getStaticProps, use absolute URLs in fetch, and prefer direct server-side code for data fetching in production builds.

The above is the detailed content of Why Do I Get Fetch Errors During My Next.js Static Website Production Build?. For more information, please follow other related articles on the PHP Chinese website!