interface ICard { expire: Function maskPreview: string preview: Function } export const card: ICard = { expire: c => ({ expiry_month: c.expiry_month || new Date(c.expires_at).getMonth() + 1, expiry_year: c.expiry_year || new Date(c.expires_at).getFullYear() }), maskPreview: 'XXXX XXXX XXXX', preview: value => `${card.maskPreview} ${value}` }