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JS
JavaScript error

TypeError

The JavaScript exception "can't access private field or method: object is not the right class" or "can't set private field: object is not the right class" occurs when a private field or method is get or set on an object that does not have this private element defined.

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: Cannot read private member #x from an object whose class did not declare it (V8-based)
As listed by MDN Web Docs
TypeError: Cannot write private member #x to an object whose class did not declare it (V8-based)
As listed by MDN Web Docs
TypeError: can't access private field or method: object is not the right class (Firefox)
As listed by MDN Web Docs
TypeError: can't set private field: object is not the right class (Firefox)
As listed by MDN Web Docs
TypeError: Cannot access invalid private field (evaluating 'this.#x') (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 2026-09-25T01:48:37.273Z.