util-joinElements.tsx

/** Determines value is not undefined or null. */
export const isValue = <T>(value: T | undefined | null): value is T =>
  (value as T) !== undefined && (value as T) !== null;

export function JoinElements(elements: ReactNode[]) {
  return elements.reduce((prev, curr) =>
    !isValue(curr) ? prev : [prev, ', ', curr]
  );
}