嵌套对象数组的连接元素

Question

我有以下数组：

[
  {
    "OrderID": 1,
    "OrderDetails": [
      {
        "OrderDetailID": 7,
    "ProductCode": "E456",
        "Quantity": 1,
      },
      {
        "OrderDetailID": 8,
    "ProductCode": "E888",
        "Quantity": 2
      }
    ],
    "OrderDate": "8/1/2018"
  },
  {
    "OrderID": 2,
    "OrderDetails": [
      {
        "OrderDetailID": 9,
    "ProductCode": "N522",
        "Quantity": 3
      }
    ],
    "OrderDate": "10/1/2018"
  }
]

使用JavaScript，我需要将所有productCodes连接到一个字符串中，以便结果应如下所示：

E456;E888;N522

我尝试使用map函数来获取OrderDetails，并且能够这样做。但是当我再次像下面那样链接map函数时，details变量总是返回undefined，所以我什至不能调用join函数来进行串联：

var details = this.orderData.map(function(i) {
     return {
         detail: i.OrderDetails
     }}).map(function(j) {
        return {
           x: j.detail.ProductCode
        }});

Answer 1

使用.reduce代替.map，将每个ProductCode推入累加器数组，然后通过;加入：

const input = [{
    "OrderID": 1,
    "OrderDetails": [{
        "OrderDetailID": 7,
        "ProductCode": "E456",
        "Quantity": 1,
      },
      {
        "OrderDetailID": 8,
        "ProductCode": "E888",
        "Quantity": 2
      }
    ],
    "OrderDate": "8/1/2018"
  },
  {
    "OrderID": 2,
    "OrderDetails": [{
      "OrderDetailID": 9,
      "ProductCode": "N522",
      "Quantity": 3
    }],
    "OrderDate": "10/1/2018"
  }
];
const productCodes = input.reduce((a, { OrderDetails }) => {
  a.push(...OrderDetails.map(({ ProductCode }) => ProductCode));
  return a;
}, []);
console.log(productCodes.join(';'));

或者，在较新的浏览器上或使用polyfill，您可以使用flatMap进一步降低它：

const productCodes = input.flatMap(
  ({ OrderDetails }) => OrderDetails.map(
    ({ ProductCode }) => ProductCode
  )
);

const input = [{
    "OrderID": 1,
    "OrderDetails": [{
        "OrderDetailID": 7,
        "ProductCode": "E456",
        "Quantity": 1,
      },
      {
        "OrderDetailID": 8,
        "ProductCode": "E888",
        "Quantity": 2
      }
    ],
    "OrderDate": "8/1/2018"
  },
  {
    "OrderID": 2,
    "OrderDetails": [{
      "OrderDetailID": 9,
      "ProductCode": "N522",
      "Quantity": 3
    }],
    "OrderDate": "10/1/2018"
  }
];
const productCodes = input.flatMap(
  ({ OrderDetails }) => OrderDetails.map(
    ({ ProductCode }) => ProductCode
  )
);
console.log(productCodes.join(';'));

Answer 2

const arr=[{OrderID:1,OrderDetails:[{OrderDetailID:7,ProductCode:"E456",Quantity:1},{OrderDetailID:8,ProductCode:"E888",Quantity:2}],OrderDate:"8/1/2018"},{OrderID:2,OrderDetails:[{OrderDetailID:9,ProductCode:"N522",Quantity:3}],OrderDate:"10/1/2018"}];

const resp = arr.map(x => x.OrderDetails.map(y => y.ProductCode).join(';')).join(';');

console.log(resp)