addOrThrow

addOrThrow(target, value)

Adds a value to the target set and returns a new set. If the value already exists in the set, throws an error.

data-first

addOrThrow(new Set([1, 2]), 3); // Set([1, 2, 3])
addOrThrow(new Set([1, 2]), 2); // throws FnError

data-last

pipe(new Set([1, 2]), addOrThrow(3)); // Set([1, 2, 3])
pipe(new Set([1, 2]), addOrThrow(2)); // throws FnError