napi add finalizer

napi_status napi_add_finalizer(napi_env env,
                               napi_value js_object,
                               void* native_object,
                               napi_finalize finalize_cb,
                               void* finalize_hint,
                               napi_ref* result);

• [in] env: The environment that the API is invoked under.
• [in] js_object: The JavaScript object to which the native data will be attached.
• [in] native_object: The native data that will be attached to the JavaScript object.
• [in] finalize_cb: Native callback that will be used to free the native data when the JavaScript object is ready for garbage-collection. [napi_finalize][] provides more details.
• [in] finalize_hint: Optional contextual hint that is passed to the finalize callback.
• [out] result: Optional reference to the JavaScript object.

Returns napi_ok if the API succeeded.

Adds a napi_finalize callback which will be called when the JavaScript object in js_object is ready for garbage collection. This API is similar to napi_wrap() except that:

• the native data cannot be retrieved later using napi_unwrap(),
• nor can it be removed later using napi_remove_wrap(), and
• the API can be called multiple times with different data items in order to attach each of them to the JavaScript object, and
• the object manipulated by the API can be used with napi_wrap().

Caution: The optional returned reference (if obtained) should be deleted via [napi_delete_reference][] ONLY in response to the finalize callback invocation. If it is deleted before then, then the finalize callback may never be invoked. Therefore, when obtaining a reference a finalize callback is also required in order to enable correct disposal of the reference.