JavaScript 将 id 从一个对象数组映射到另一个对象数组

Question

const rowData = [];
const arr1 = [{
    "bId": "F1.1.4",
    "bName": "Mercedes",
    "cId": "150494",
    "cName": "Benz",
    "flag": "Maintain"
  },
  {
    "bId": "F1.1.4",
    "bName": "Ford",
    "cId": "150744",
    "cName": "Mustang",
    "flag": "Maintain"
  },
  {
    "bId": "F1.1.4",
    "bName": "Volkswagon",
    "cId": "4961",
    "cName": "Polo",
    "flag": "Maintain"
  },
  {
    "bId": "F1.1.5",
    "bName": "Isdera",
    "cId": "N/A",
    "cName": "Isdera",
    "flag": "Test"
  }
]

const arr2 = [{
    "cId": "150494",
    "flag": "Decommission"
  },
  {
    "cId": "150744",
    "flag": "Invest"
  },
  {
    "cId": "4961",
    "flag": "Pending"
  }
]

for (let i = 0; i < arr1.length; i++) {
  const obj = {
    custId: arr1[i].cId,
    custName: arr1[i].cName,
    bId: arr1[i].bId,
    bufName: arr1[i].bName,
    impFlag: arr2.filter(({cId}) => cId === arr1[i].cId).map(({flag}) => (flag)).toString()
  };
  rowData.push(obj);
}
console.log(rowData)

嗨，我正在检查

cId

中的

arr2

是否存在于

arr1

中，并基于此我更新存在 cId 的标志，但对于 arr2 中不存在的其余值，impFlag即将到来

""

。它应该与 arr1 中的相同。我不知道如何相应地添加条件？？

Answer 1

由于

""

是您通过调用 Array.prototype.toString()

 获得的唯一 

falsy 值，因此您可以使用

||

(OR) 运算符在没有匹配标志时提供默认值，例如：

arr2.filter(...).map(...).toString() || arr1[i].flag

上面，当

.toString()

产生假

""

值时，

||

运算符的右侧将用作结果。

const rowData = [];
const arr1 = [{
    "bId": "F1.1.4",
    "bName": "Mercedes",
    "cId": "150494",
    "cName": "Benz",
    "flag": "Maintain"
  },
  {
    "bId": "F1.1.4",
    "bName": "Ford",
    "cId": "150744",
    "cName": "Mustang",
    "flag": "Maintain"
  },
  {
    "bId": "F1.1.4",
    "bName": "Volkswagon",
    "cId": "4961",
    "cName": "Polo",
    "flag": "Maintain"
  },
  {
    "bId": "F1.1.5",
    "bName": "Isdera",
    "cId": "N/A",
    "cName": "Isdera",
    "flag": "Test"
  }
]

const arr2 = [{
    "cId": "150494",
    "flag": "Decommission"
  },
  {
    "cId": "150744",
    "flag": "Invest"
  },
  {
    "cId": "4961",
    "flag": "Pending"
  }
]

for (let i = 0; i < arr1.length; i++) {
  const obj = {
    custId: arr1[i].cId,
    custName: arr1[i].cName,
    bId: arr1[i].bId,
    bufName: arr1[i].bName,
    impFlag: arr2.filter(({cId}) => cId === arr1[i].cId).map(({flag}) => (flag)).toString() || arr1[i].flag
  };
  rowData.push(obj);
}
console.log(rowData)