docs.

ops set of callbacks required by the device, docs provides an only example for one specific filesystem to write types to each separately will probably be an overkill

docs

e in callback is en error, unfortunately in this case docs does not day what the error can be (basically everything, number with error code, JS Error or some object)

docs

there is no definition of the return type, and in an example, the function does not return anything, but after reading the docs there are some sentences like: The parent folder, either as a path (e.g. ‘/usr/lib’) or an object previously returned from a FS.mkdir() etc. so I don't think there is a better way of specifying the type

I don't think this works. In the typescript types, they just have defined a few variables, but we don't know what values they have

If we don't use it, we don't have to type it more specificly, but we can use mixed instead of any without any loss

This will make it a bit less ergonomic, but worst case, we can cast to any inside of the callback

Should this be void?

I think that based on the typescript types it should be like this (also in the other readFile and writeFile)