In versions of node before that of 8.x if I wanted to make a node js method return a promise rather than having to deal with callbacks I would have to use some kind of user land module to promisify that method, do so manually with the Promise constructor, or use a dependency that does so out of the box such as with fs-extra for example. However in versions of node 8+ there is now the util.promisify method that can be used to promisify one of these callbacks.
The util.promisify method can be used with any of the methods in nodejs that make use of the usual nodejs style callback that passes a error as the first argument and the something more after that in the event that things go well. Many examples of this kind of method exist in the file system module for example
In the new node 10.x LTS release it looks like there is now and experimental promise api of the file system module, so it is evident that eventually one will not even need to bother with this any more as well, and out of the box file system methods will work just like that of what I have come to know when using fs-extra.