Is it TypeScript's return type a double arrow (Observable)?

I'm having a hard time understanding this:

const loadData: (detailsStore: RecipeDetailsStore) => (source$: Observable<string>) => Observable<RecipeDetails>

How should I interpret this?

My understanding is:

loadData is a function that takes an argument of type RecipeDetailsStore, and then it returns another function that accepts a parameter named source$ of type Observable<string>. Ultimately, the return type is an Observable of type RecipeDetails? But I'm not entirely certain.

Or does it mean that loadData is a function with a return type of 

(detailsStore: RecipeDetailsStore) => (source$: Observable<string>) => Observable<RecipeDetails>
?

The double arrow is throwing me off. What does it signify?

I attempted to ask ChatGPT for help, but even ChatGPT seems confused and trapped in an infinite loop (a situation I've never encountered before with ChatGPT).

angulartypescriptrxjs

Answer №1

Your initial understanding is accurate.

The alternative explanation suggests that a third arrow is necessary, resulting in a code snippet resembling this:

let fetchData: () => (infoStorage: RecipeInfoStorage) => (input$: Observable<string>) => Observable<RecipeDetails>

As @John Montgomery pointed out, you must provide an assignment when using const. Consider using let as an alternative;

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