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JS
JavaScript error

TypeError

The JavaScript exception "is not a non-null object" occurs when an object is expected somewhere and wasn't provided. null is not an object and won't work.

Reference entryJavaScriptFetched
This is a reference entry from MDN Web Docs. A full explanation with fixes has not been written yet.

The error messages

TypeError: Property description must be an object: x (V8-based)
As listed by MDN Web Docs
TypeError: Property descriptor must be an object, got "x" (Firefox)
As listed by MDN Web Docs
TypeError: Property description must be an object. (Safari)
As listed by MDN Web Docs

Details

Category
TypeError
Severity
error
Runtime
both

Related errors

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Source: MDN Web Docs. Data fetched 2026-09-25T01:48:37.274Z.