Question 258147 in Javascript Question posted in
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JavaScript map id from one array of object to another

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)

Hi, I’m checking if cId in arr2 is present in arr1 and based on it I’m updating the flag for which cId is present, but for the remaining values which are not present in arr2, impFlag is coming as "". It should remain the same as in arr1. I’m not sure how to add conditions accordingly??

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2

Answers


  1. 0

    Since "" is the only falsy value that you’ll get from calling Array.prototype.toString(), you can use the || (OR) operator to provide a default value when there are no matching flags, eg:

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

    Above, when .toString() results in a falsy "" value, the right-hand side of the || operator is used as the result instead.

    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)

    Personally, I would write this logic as below. As you’re performing a mapping operator, .map() is a good tool for this:

    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" } ];


const cIdMap = new Map(arr2.map(({cId, flag}) => [cId, flag]));

const rowData = arr1.map((obj) => ({
  custId: obj.cId,
  custName: obj.cName,
  bId: obj.bId,
  bufName: obj.bName,
  impFlag: cIdMap.get(obj.cId) ?? obj.flag
}));

console.log(rowData)
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  2. 0

    You could use Array.reduce method instead

    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"
  }
];

const result = arr1.reduce((c,d)=>{
   const id = d.cId;
   const flag = arr2.find(d=> d.cId == id)?.flag;
   flag && (d.flag = flag);
   console.log(flag)
   c.push({...d})
   return c;
},[]);

console.log(result)
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