Setear objeto json usando el campo _id

data.json

[
    {
    "_id": 7,
    "assignmentDateFormats": {},
    "idAssignment": 29,
    "assignmentDate": {},
    "currentAssignment": 0,
    "idEmmployee": 24,
    "idDwEnterprise": 85,
    "idStock": 1,
    "idAccessLevel": 1,
    "dwEnterprises": {
      "_id": 8,
      "idDwEnterprise": 85,
      "idBrand": 0,
      "idGbranch": 0,
      "idGroup": 1,
      "idDistributor": 9,
      "idRegion": 3,
      "idBranch": 79,
      "idArea": 5,
      "budgetable": 1,
      "group": 3,
      "distributor": {
        "idDistributor": 9,
        "distributorName": "BID GROUP",
        "acronyms": "BID",
        "hasStock": 1
      },
      "region": {
        "idRegion": 3,
        "regionName": "CENTRO"
      },
      "branch": {
        "idBranch": 79,
        "branchName": "CORPORATIVO",
        "branchShort": "CORPORATIVO",
        "location": "CORPORATIVO- TORRE VIRREYES",
        "address": null,
      },
      "area": {
        "idArea": 5,
        "areaName": "RRHH"
      },
      "budgetMonthBranchList": null,
      "dwEmployeesList": null
    },
    "employee": 4,
    "stocks": null
  },
  {
    "_id": 9,
    "assignmentDateFormats": {},
    "idAssignment": 28,
    "assignmentDate": {},
    "currentAssignment": 0,
    "idEmmployee": 19,
    "idDwEnterprise": 85,
    "idStock": 1,
    "idAccessLevel": 1,
    "dwEnterprises": 8,
    "employee": {
      "_id": 10,
      "firstName": "Rafael",
      "middleName": "",
      "parentalLast": "Viveros",
      "motherLast": "Badillo",
      "rfc": "_3",
      "claveSap": "_3",
      "curp": null,
      "imss": null,
      "infonavitNumber": null,
      "mail": null,
      "employeeType": null,
      "contractType": null,
      "salary": 0.00,
      "state": null,
      "joinDateFormats": {},
      "bithDayFormats": {},
      "idEmployee": 19,
      "employeeNumber": null,
      "joinDate": {},
      "status": 1,
      "birthPlace": null,
      "birthday": {},
      "street": null,
      "exteriorNumber": null,
      "interiorNumber": null,
      "colonia": null,
      "city": null,
      "postcode": null,
      "cellPhone": null,
      "fatherName": null,
      "motherName": null,
      "dwEmployeesList": null,
      "employeesAccountsList": null
    },
    "stocks": null
]

json_id.js

fetchStockAssignmentsRecord: function (article) {
    this.$http.get(
        ROOT_URL + "/stock/" + article.idStock + "/assignments/record"
    ).success(function(data) {
        var jsonObjectIndex = {};
        data.forEach(function (el) {
            if (isNaN(el.dwEnterprises)) {
                jsonObjectIndex[el.dwEnterprises._id] = el.dwEnterprises;
            } else {
                el.dwEnterprises = jsonObjectIndex[el.dwEnterprises];
            }
            if (isNaN(el.employee)) {
                jsonObjectIndex[el.employee._id] = el.employee;
            } else {
                el.employee = jsonObjectIndex[el.employee];
            }
        });
    });
}