The primary usecase (which happens to me fairly frequently in Javascript) is when you need to operate on a native or library data structure with some function o

The primary usecase (which happens to me fairly frequently in Javascript) is when you need to operate on a native or library data structure with some function other than its built-in methods. Some people also find it easier to program in an FP style (separating data and functions) in their app code. It seems to be a matter of neurodiversity.