Sample TypeScript File

// Sample TypeScript module — samplefiles.com
export interface Customer {
  readonly id: number;
  name: string;
  balance: number;
  tags?: string[];
}

export const isVip = (c: Customer): boolean => c.balance >= 10_000;

export function totalBalance(customers: readonly Customer[]): number {
  return customers.reduce((sum, c) => sum + c.balance, 0);
}

const customers: Customer[] = [
  { id: 1, name: 'Ada', balance: 12_500 },
  { id: 2, name: 'Grace', balance: 830.5, tags: ['new'] },
  { id: 3, name: 'Linus', balance: 10_000 },
];

for (const c of customers) {
  console.log(`${c.name.padEnd(6)} ${c.balance.toFixed(2).padStart(10)} ${isVip(c) ? 'VIP' : ''}`);
}
console.log(`Total: ${totalBalance(customers).toFixed(2)}`);