namespace Membership {
  export function AddMember(name: string) {
    console.log(`Adding new member ${name}.`);
  }

  export namespace Cards {
    export function IssueCard(memberNumber: number) {
      console.log(`Issuing new card for member #${memberNumber}.`);
    }
  }
}

Membership.AddMember('Garrett');
Membership.Cards.IssueCard(1234);