Group Orders by Customer.md

Group Orders by Customer.md

💡 Problem: Group Orders by Customer

Given an array of orders like this:

type Order = {
  orderId: number;
  customerId: number;
  amount: number;
};

const orders: Order[] = [
  { orderId: 1, customerId: 1, amount: 200 },
  { orderId: 2, customerId: 2, amount: 100 },
  { orderId: 3, customerId: 1, amount: 300 },
  { orderId: 4, customerId: 3, amount: 150 },
  { orderId: 5, customerId: 2, amount: 400 },
];

✅ Requirements:

1. Write a function groupOrdersByCustomer that takes the orders array and returns an object with the following structure:

{
  1: { totalAmount: 500, orders: [1, 3] },
  2: { totalAmount: 500, orders: [2, 5] },
  3: { totalAmount: 150, orders: [4] }
}

🎯 Bonus (optional):

• Implement it with TypeScript types (e.g. Record<number, { ... }>).
• Add a function getTopCustomer() that returns the customerId with the highest total spending.

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🧠 Evaluation Criteria

Skill	Criteria
Array methods	Uses reduce, map, filter appropriately
Object manipulation	Correctly accesses and updates dynamic objects
TypeScript	Properly defines types for return value (if required)
Logical thinking	Understands how to group and summarize data
Clean code	Uses clear variable and function names, readable logic

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🧪 Expected Output

groupOrdersByCustomer(orders);
// =>
// {
//   1: { totalAmount: 500, orders: [1, 3] },
//   2: { totalAmount: 500, orders: [2, 5] },
//   3: { totalAmount: 150, orders: [4] }
// }

getTopCustomer(orders);
// => 1 or 2 (either is acceptable if totals are equal)

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If you’d like more 20-minute live-coding challenges, I can provide more advanced ones like:

• Flatten a nested object
• Merge two arrays of objects by a common key
• Manually implement a groupBy function

Would you like a more advanced challenge next?