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TypeError: Cannot read properties of undefined (reading 'map')

Last checked 2026-10-17 · 3 fixes · reviewed answer

Likely causes

1. A variable expected to contain an array or list is undefined because data was not loaded or fetched correctlymost likely
2. An API response or function return value did not provide the expected array structurepossible
3. A coding mistake where the wrong variable name is used before calling .mapless likely

How to fix it

1. Check the browser or console logs for more context around the errorSafe

   Open the developer console in the browser or application to see the exact line of code causing the issue and any related messages.

2. Inspect the variable before the .map callSafe

   Add a temporary check or console log to confirm the variable's value right before the error line to see if it is undefined.

3. Add a guard to handle undefined valuesChanges settings

   Update the code to verify the variable is an array before calling .map, for example by using optional chaining or a default empty array.

If that didn't fix it

The application will keep crashing or failing at that point until the code is corrected to handle missing data.

When to see a technician

Contact the software developer or support team responsible for the application if this error appears in a live website or program.

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