But this is the problem with basically every functional programming article that makes it's way to HN. As a thought experiment it makes sense but it's not transferrable to the real world.
Like take the log out action as an example. Mid request we are going to have to change the state from a user logged in to a user logged out. Otherwise when we render the home screen, as an example, they'll see the logged in version instead of the anonymous user one.
And realistically we want need a transition state to show a successfully logged out message since we do not want that message to show the next time they come. So the whole sequence for this simple action is:
Old State -> Intermediate State -> Render Response -> New State for the next request.
So we have to change state a couple times and pass that along.
And then how do we deal with stuff that's actually state. Like a database or whatever. Are we really passing that as a function parameter so that 10 calls deep can use it?
And what happens 6 months in when we want a caching layer? Do we go back and edit every single function to accept a Redis argument now?
Realistically, no. We have some sort of config or server object that we pass along. So we have an object that contains all of our server state that gets passed to most functions. How is that better than a single global variable holding that state accessible everywhere in the application?
Like take the log out action as an example. Mid request we are going to have to change the state from a user logged in to a user logged out. Otherwise when we render the home screen, as an example, they'll see the logged in version instead of the anonymous user one.
And realistically we want need a transition state to show a successfully logged out message since we do not want that message to show the next time they come. So the whole sequence for this simple action is:
Old State -> Intermediate State -> Render Response -> New State for the next request.
So we have to change state a couple times and pass that along.
And then how do we deal with stuff that's actually state. Like a database or whatever. Are we really passing that as a function parameter so that 10 calls deep can use it?
And what happens 6 months in when we want a caching layer? Do we go back and edit every single function to accept a Redis argument now?
Realistically, no. We have some sort of config or server object that we pass along. So we have an object that contains all of our server state that gets passed to most functions. How is that better than a single global variable holding that state accessible everywhere in the application?