What is causing the "TypeError: Cannot convert undefined or null to object" error on multiple pages in Webflow?

The "TypeError: Cannot convert undefined or null to object" error in Webflow typically occurs due to JavaScript issues, such as trying to access properties of null or undefined elements. Follow these steps to troubleshoot and fix the issue.

1. Check for Missing Elements

• If your custom JavaScript references an element by document.querySelector or getElementById, ensure the element actually exists on the page.
• Use console.log(document.querySelector('your-selector')) in DevTools Console to confirm the element is found.

2. Review Custom JavaScript Code

• Go to Page Settings or Project Settings > Custom Code, and inspect any custom scripts.
• Look for code that directly interacts with DOM elements using object.property where the object could be null or undefined.

3. Add Defensive Checks in JavaScript

• Before accessing an object's properties, verify it exists:
• Use optional chaining (?.), e.g., document.querySelector('.className')?.textContent.
• Check explicitly, e.g.,
  ```js
  let element = document.querySelector('.className');
  if (element) { element.textContent = "Hello"; }
  ```

4. Disable Third-Party Scripts

• If you're loading external JavaScript (e.g., jQuery, analytics, plugins), temporarily disable them and check if the error persists.
• In DevTools Console, look for script source URLs that might point to external issues.

5. Debug with DevTools Console

• Open Chrome DevTools (F12) > Console.
• Look for the exact file name and line number where the error occurs.
• If the error points to Webflow’s native scripts, it could be an issue with dynamic elements added at runtime.

6. Test in Incognito Mode & Different Browsers

• Browser extensions can interfere with scripts. Test in Incognito Mode with extensions disabled.
• If the issue is browser-specific, check for rendering differences (Safari, Chrome, Firefox).

Summary

This error happens when JavaScript tries to manipulate a missing or undefined object. Validate elements exist before interacting with them, and check for faulty third-party scripts. Use DevTools Console for debugging and isolate the issue by disabling custom code if needed.