replacing the document with null is not removing the document

I believe the behavior of removing / should be left to the implementation as it cannot be semantically defined by json patch

In https://github.com/JSON8/patch I return undefined

In https://github.com/JSON8/patch I return undefined

While that is compliant with the spec, it is unfortunate, as it breaks the expectation that the result remains a valid JSON document. I would recommend you change it to return null.

I believe the behavior we want should be explicit rather than implicit or unspecified. The spec defines the semantics of all that it defines. In the meantime, having divergence in implementations' behavior is unfortunate.

JSON.stringify(undefined) returns "undefined" so the program won't break and it let the user decides what to do for the remove / case.

Anyway, this repo contains JSON Patch tests and since your proposed behavior is not specified I'd 👎

I'm not fond of the idea that removing the object converts it to the 9-character string "undefined" by default.