How to make the fs.readDir to read a folder from a relative path? where the root is not the entry point of the node process

I have the fs.readDir in file "/subfolder/a" and the file "/subfolder/a" is called from "/b". When I run the fs.readDir it shows me the files in the "/" which is b. I would like to know if there is anyway to "say" to the fs.readDir to set as it's root to be "/subfolder/" instead of "/".

Update: Of course I could use the path relative to the node entry point, but I would like to use something like "./" (current folder) from the file "/subfolder/a" and get the contents of the folder "/subfolder/" and not the folder "/".