如何展平并合并嵌套数组中的子数组？附JavaScript示例数据

Got it, let's work through this. You need to flatten those nested transactions arrays under each product and merge them into a single collection—either with their associated purchase/product details (which is usually the more practical use case) or just the raw transaction entries. Here are both approaches:

Option 1: Keep Purchase & Product Context (Recommended) #

If you want each transaction entry to retain information about which purchase and product it belongs to, use nested flatMap calls combined with map to attach the context:

let data = [
 { "purchase_id": 1, "product": [ { "name": "A", "id": 1, "transactions": [ { "price": 5, "qty": 2 }, { "price": 10, "qty": 2 } ] }, { "name": "B", "id": 2, "transactions": [ { "price": 3, "qty": 4 } ] } ] },
 { "purchase_id": 2, "product": [ { "name": "C", "id": 3, "transactions": [ { "price": 5, "qty": 2 } ] }, { "name": "D", "id": 4, "transactions": [ { "price": 3, "qty": 4 } ] } ] }
];

const flattenedTransactions = data.flatMap(purchase => 
  purchase.product.flatMap(product => 
    product.transactions.map(transaction => ({
      purchase_id: purchase.purchase_id,
      product_name: product.name,
      product_id: product.id,
      ...transaction // Spread the transaction's price and qty
    }))
  )
);

console.log(flattenedTransactions);

Output: #

[
  { purchase_id: 1, product_name: 'A', product_id: 1, price: 5, qty: 2 },
  { purchase_id: 1, product_name: 'A', product_id: 1, price: 10, qty: 2 },
  { purchase_id: 1, product_name: 'B', product_id: 2, price: 3, qty: 4 },
  { purchase_id: 2, product_name: 'C', product_id: 3, price: 5, qty: 2 },
  { purchase_id: 2, product_name: 'D', product_id: 4, price: 3, qty: 4 }
]

Option 2: Merge Raw Transactions Only #

If you don't need the purchase/product context and just want a flat array of all transaction objects, simplify the code to just nested flatMap calls:

const allRawTransactions = data.flatMap(purchase => 
  purchase.product.flatMap(product => product.transactions)
);

console.log(allRawTransactions);

Output: #

[
  { price: 5, qty: 2 },
  { price: 10, qty: 2 },
  { price: 3, qty: 4 },
  { price: 5, qty: 2 },
  { price: 3, qty: 4 }
]

Quick Breakdown: #

• flatMap is ideal here because it maps over elements and flattens the resulting array by one level—no extra nested arrays cluttering the final output.
• For the context-rich version, map lets us combine each transaction with its parent product and purchase data using object spread (...transaction) to preserve the original transaction fields.

内容的提问来源于stack exchange，提问作者Pengguna