How to type functions.

[ff6347]

I'd like to ask a question/start a discussion about typing functions.
I saw that you (@vogelino) tend to write signatures like this:

const setVisibleMapLayer = (
  type: StoreProps['visibleMapLayer']
): { visibleMapLayer: StoreProps['visibleMapLayer'] } => {
  return {
    visibleMapLayer: type,
  };
};

giessdenkiez-de/src/state/Actions.tsx

Line 13 in 612d5f0

const setVisibleMapLayer = (

Where I like to write them like this:

const setVisibleMapLayer: (
  type: StoreProps['visibleMapLayer']
) => { visibleMapLayer: StoreProps['visibleMapLayer'] } = (type) => {
  return {
    visibleMapLayer: type,
  };
};

Why do I prefer the one over the other?

If I would have to share this function signature with another function I just could do extract it by copying it into a type and I'm done.

type SetterFunc =  (
  type: StoreProps['visibleMapLayer']
) => { visibleMapLayer: StoreProps['visibleMapLayer'] };

const setVisibleMapLayer: SetterFunc= (type) => {
  return {
    visibleMapLayer: type,
  };
};

In your way of typing it the description of the types and the implementation are tightly coupled. Any reason why you write it your way?

---

Another thing I do often is use the function keyword on top level functions.

function(a: number): number {
return a;
}

So my rule is to only use const thing = () … if I'm in a closure and use function in the global scope. Any reason why you don't use function at all?

@lucasoeth @dnsos I'd also like to hear your opinion about this.

---

Lets assume that all the things said in #293 are below.

[ff6347]

…
@vogelino

Common, could we not talk about your way/ my way?

Yes. Sorry.

An can you elaborate on why do you think it is easier to digest?

I think if the reader is used to that kind of signature they can scan from : until = to see the definition. Since I'm used to it I had problems reading the tighter coupled way at first sight.

[vogelino]

I agree, it is a question of habit. I'm not too religious about it.

[ff6347]

me neither. We currently have more of tightly coupled signatures. Let's keep it that way.