#TypeError: Cannot read properties of undefined (reading 'startsWith')

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wind kettleBOT
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Hi @rare isle. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base. :wave:

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The error TypeError: Cannot read properties of undefined (reading 'startsWith') is not explicitly documented in the provided knowledge sources. However, similar errors (such as "Cannot read properties of undefined (reading 'call')" or "bind") are frequently reported in Next.js projects, especially after deployments or when using certain runtimes or middleware.

Based on the patterns in the knowledge sources, these types of errors often occur due to:

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What you can do:

  • If this error appears after a deployment, try a hard refresh in the browser.
  • Check if you are using any Node.js-specific APIs in middleware or edge runtime code.
  • Ensure all required packages and configuration files are present and correctly set up.
  • If you are using Vercel, make sure Skew Protection is enabled, but be aware it cannot fully prevent these issues.
  • If the error persists, try to catch it globally and prompt the user to refresh the page.

If you can provide more context (such as a stack trace or code snippet), I may be able to give more targeted advice. But based on the knowledge sources, these are the most common causes and mitigations for similar errors.

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:

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@rare isle Kapa.ai is still learning and improving, please let me know how I did by reacting below.

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Let me check the knowledge base for you again. Give me one moment! :books:

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The error message you are seeing:

Error occurred prerendering page "/competition-management". Read more: <https://nextjs.org/docs/messages/prerender-error>
TypeError: Cannot read properties of undefined (reading 'startsWith')
...
Export encountered an error on /(authenticated)/competition-management/page: /competition-management, exiting the build.

is a type of prerendering error that occurs during the Next.js build process, specifically when statically generating pages. According to the knowledge sources, similar errors often stem from:

  • Undefined Variables or Data: The error Cannot read properties of undefined (reading 'startsWith') suggests that somewhere in your code (likely in the /competition-management page or its dependencies), you are calling .startsWith on a variable that is undefined during the build. This can happen if you are expecting certain data to be present at build time, but it is not available or is only available at runtime.

  • Environment Variables or Configuration Issues: Several users have reported that missing environment variables (especially when deploying to Vercel) can cause prerendering to fail with similar errors. For example, if you are using a service like Supabase or NextAuth and the required environment variables are not set in your Vercel project, the build can fail with unrelated-looking errors. Make sure all necessary environment variables are set in your Vercel project settings, not just in .env.local but also in .env if needed (source).

  • Circular Dependencies or Import Issues: Circular dependencies can also cause unexpected undefined values during the build, leading to errors like this. Review your imports and try to eliminate any circular references (source).

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  • Node.js Version or Package Manager Issues: Some users have reported that certain Node.js versions or using pnpm instead of npm can cause build issues. Try deleting node_modules and your lock file, then reinstalling dependencies with npm instead of pnpm to see if the error message becomes clearer or the issue is resolved (source).

What you can do:

  1. Check for undefined variables: Review the code in /competition-management and its dependencies for any usage of .startsWith and ensure the variable is always defined.
  2. Verify environment variables: Make sure all required environment variables are set in your Vercel project settings.
  3. Check for circular dependencies: Refactor any circular imports that might be causing undefined values.
  4. Try a clean install: Delete node_modules and your lock file, then reinstall dependencies.
  5. Switch package manager: If using pnpm, try switching to npm for the build process to see if the error changes or resolves.

If after these steps the issue persists, try to isolate the code in /competition-management that uses .startsWith and add checks to ensure the variable is defined before calling the method.

The knowledge sources do not provide a single definitive fix for this specific error, but the above steps are based on similar issues and their resolutions as reported by other Next.js users (source) (source).

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:

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@rare isle Kapa.ai is still learning and improving, please let me know how I did by reacting below.

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Let me check the knowledge base for you again. Give me one moment! :books:

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Yes, this issue can occur because of the code you shared. According to the knowledge sources, if process.env.NEXT_PUBLIC_APPWRITE_ENDPOINT is not defined at build time, then appwriteEndpoint will be undefined. When you try to create a new URL(appwriteEndpoint), it will throw an error because undefined is not a valid argument for the URL constructor. This can result in a build-time error such as TypeError: Cannot read properties of undefined (reading 'startsWith'), since the URL constructor internally calls .startsWith on its input.

This pattern is similar to other issues reported in the knowledge sources, where missing or undefined environment variables cause build failures during prerendering or static generation (Error occurred prerendering page "/_not-found").

How to fix:
You should ensure that process.env.NEXT_PUBLIC_APPWRITE_ENDPOINT is always defined at build time, especially in your Vercel environment variables. Alternatively, you can add a safer check before using the URL constructor:

const appwriteHostname = appwriteEndpoint
  ? new URL(appwriteEndpoint).hostname
  : "";

But if appwriteEndpoint is undefined, you should avoid calling new URL() altogether.

Summary:
Yes, the error can be caused by this code if the environment variable is missing or undefined during the build, leading to an invalid call to new URL(), which in turn triggers the .startsWith error you are seeing (Error occurred prerendering page "/_not-found").

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:

#

@rare isle Kapa.ai is still learning and improving, please let me know how I did by reacting below.

#

Let me check the knowledge base for you again. Give me one moment! :books:

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Based on the knowledge sources, yes, this code can also cause the issue if any of the environment variables (NEXT_PUBLIC_APPWRITE_ENDPOINT, NEXT_PUBLIC_APPWRITE_BUCKET_ID, or NEXT_PUBLIC_APPWRITE_PROJECT_ID) are undefined at build time. When you construct the URL:

const getBannerImageURL = `${process.env.NEXT_PUBLIC_APPWRITE_ENDPOINT}/storage/buckets/${process.env.NEXT_PUBLIC_APPWRITE_BUCKET_ID}/files/${getSelectedCompetition.$id}/view?project=${process.env.NEXT_PUBLIC_APPWRITE_PROJECT_ID}`;

If, for example, NEXT_PUBLIC_APPWRITE_ENDPOINT is undefined, the resulting string will start with "undefined/storage/buckets/...". Later, if you use this value in a context that expects a valid URL (such as passing it to the URL constructor or a fetch/image component), it can trigger errors like Cannot read properties of undefined (reading 'startsWith'), because the underlying code may try to call .startsWith on undefined.

Key points from the knowledge sources:

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How to avoid this:

  • Make sure all required environment variables are set in your deployment environment before building.
  • Optionally, add checks in your code to handle missing environment variables gracefully, for example:
if (
  !process.env.NEXT_PUBLIC_APPWRITE_ENDPOINT ||
  !process.env.NEXT_PUBLIC_APPWRITE_BUCKET_ID ||
  !process.env.NEXT_PUBLIC_APPWRITE_PROJECT_ID
) {
  throw new Error("Missing required environment variables for Appwrite configuration.");
}

Summary:
If any of the referenced environment variables are missing or undefined at build time, this code can cause the type of error you are seeing during prerendering or static generation (Bundling Environment Variables for the Browser).

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: