addOrElse

addOrElse(target, value, orElse)

Adds a value to the target set and returns a new set. If the value already exists in the set, calls the orElse function with the target set and returns its result.

data-first

addOrElse(new Set([1, 2]), 3, (set) => set.size); // Set([1, 2, 3])
addOrElse(new Set([1, 2]), 2, (set) => set.size); // 2

data-last

pipe(
    new Set([1, 2]),
    addOrElse(3, (set) => set.size),
); // Set([1, 2, 3])

pipe(
    new Set([1, 2]),
    addOrElse(2, (set) => set.size),
); // 2