dinocarl

const recMerge = (objA, objB) => Object.entries(objB).reduce(
  (acc, [key, val]) => Object.assign(
    {},
    objA,
    { [key]: is(Object, val) ? recMerge(objA[key], val) : val }
  ),
  {}
);

dinocarl

type Predicate<T> = (value: T) => boolean;
type Mapper<T, R> = (value: T) => R;
type CondPair<T, R> = [Predicate<T>, Mapper<T, R>];

// recursive cond that can breaks early or returns undefined
const cond = <T, R>(
  [[pred, mapr] = [] as unknown as CondPair<T, R>, ...rest]: CondPair<T, R>[] = []
): ((val: T) => R | undefined) => (val: T): R | undefined =>
  !pred ? undefined :
  pred(val) ? mapr(val) : cond(rest)(val);