Add callOrReturn function

[aleclarson]

If the first argument is a function, call it with the remaining arguments. Otherwise, return the first argument.

Useful for flexible option values that may be a function or not.

type ExtractParameters<T> = Parameters<Extract<T, Function>>
type ExtractReturn<T> = T extends (...args: any[]) => infer Return ? Return : T

export function callOrReturn<T>(value: T, ...args: ExtractParameters<T>): ExtractReturn<T> {
  return isFunction(value) ? value(...args) : value
}

Example

declare const delay: number | ((item: object) => number)

callOrReturn(delay, item) // => number

Naming

Open to suggestions.

[aleclarson]

Too much sugar... :)