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JS
JavaScript error

TypeError

The JavaScript exception "right-hand side of 'in' should be an object" occurs when the in operator was used to search in strings, or in numbers, or other primitive types. It can only be used to check if a property is in an object.

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 use 'in' operator to search for 'x' in 'y' (V8-based & Firefox)
As listed by MDN Web Docs
TypeError: right-hand side of 'in' should be an object, got null (Firefox)
As listed by MDN Web Docs
TypeError: "y" is not an Object. (evaluating '"x" in "y"') (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.