two array one in price and productname and the second is username, quantity, productname how to group this two array in one by username using pure js?

Here's my arrays:

let prices = [
    {
        product: "p1",
        price: 100,
    },
    {
        product: "p2",
        price: 120.2,
    },
    {
        product: "p3",
        price: 120,
    },
    {
        product: "p4",
        price: 125,
    },
]

let orders = [
    {
        user: "user1",
        product: "p1",
        quantity: 2,
    },
    {
        user: "user1",
        product: "p1",
        quantity: 4,
    },
    {
        user: "user4",
        product: "p3",
        quantity: 5,
    },
    {
        user: "user4",
        product: "p4",
        quantity: 10,
    },
    {
        user: "user3",
        product: "p2",
        quantity: 10,
    },
    {
        user: "user4",
        product: "p1",
        quantity: 10,
    },
    {
        user: "user1",
        product: "p2",
        quantity: 10,
    },
    {
        user: "user3",
        product: "p2",
        quantity: 20,
    }
]

How can I group it by user so that I would get the result of:

result = [
    {
        user: "user1",
        product: [
            {
                productName: "p1",
                quantity: 6,
                itemPrice: 100,
                totalPrice: 600
            }
        ],
        total: 600
    },
    {
        user: "user4",
        product: [
            {
                productName: "p3",
                quantity: 5,
                itemprice: 120,
                totalPrice: 600
            },
            {
                productName: 'p4',
                quantity: 10,
                itemprice: 125,
                totalPrice: 1250
            }
        ],
        total: 1850
    }
]

You could find the group of customer first and then find the item and create the product of price and quantity.

For easier access of prices, you could use an object pricesByProduct.

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const
prices = [{ product: "p1", price: 100 }, { product: "p2", price: 120.2 }, { product: "p3", price: 120 }, { product: "p4", price: 125 }],
orders = [{ user: "user1", product: "p1", quantity: 2 }, { user: "user1", product: "p1", quantity: 4 }, { user: "user4", product: "p3", quantity: 5 }, { user: "user4", product: "p4", quantity: 10 }, { user: "user3", product: "p2", quantity: 10 }, { user: "user4", product: "p1", quantity: 10 }, { user: "user1", product: "p2", quantity: 10 }, { user: "user3", product: "p2", quantity: 20 }],
pricesByProduct = Object.fromEntries(prices.map(({ product, price }) => [product, price])),
result = orders.reduce((r, { user, product: productName, quantity }) => {
let customer = r.find(q => q.user === user);
if (!customer) r.push(customer = { user, product: [], total: 0 });

        let item = customer.product.find(q => q.productName === productName);
if (!item) customer.product.push(item = { productName, quantity: 0, itemPrice: pricesByProduct[productName], totalPrice: 0 });
let orderPrice = item.itemPrice * quantity;
item.quantity += quantity;
item.totalPrice += orderPrice;
customer.total += orderPrice;
return r;
}, []);
console.log(result);

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