how to find duplicates in array and merge nested data

Question

I have an object array with duplicates. The data at the root level of the objects are identical, but the nested array of objects are not. That is what I need to merge before running a lodash uniqBy or whatever function to remove the duplicates.

This is the object array with duplicates.

    [
    {
        "id": "66E175A2-A29F-4F1A-AD81-2422B1EB00F6",
        "name": "College Park / Brookhaven",
        "mktId": 0,
        "status": "Unknown",
        "code": "197D6",
        "ownershipType": null,
        "series": [
            {
                "id": "80004F2E-E3C8-4B6A-BCCC-81259AEAF22D",
                "name": "01",
                "productType": "Detached",
                "productClass": "Single Family",
                "salesStartDate": null,
                "modelOpenDate": null
            }
        ]
    },
    {
        "id": "E053E656-4D14-4F2A-AD70-A37F65195CD1",
        "name": "College Park / Hampshire",
        "mktId": 0,
        "status": "Unknown",
        "code": "316D6",
        "ownershipType": null,
        "series": [
            {
                "id": "46830FBD-CD68-4D4C-A095-FB9C3D93D01A",
                "name": "02,03",
                "productType": "Detached",
                "productClass": "Single Family",
                "salesStartDate": null,
                "modelOpenDate": null
            }
        ]
    },
    {
        "id": "E053E656-4D14-4F2A-AD70-A37F65195CD1",
        "name": "College Park / Hampshire",
        "mktId": 0,
        "status": "Unknown",
        "code": "316D6",
        "ownershipType": null,
        "series": [
            {
                "id": "1BC31692-AAB8-4A00-9D8D-9B8CF7E426E0",
                "name": "01",
                "productType": "Detached",
                "productClass": "Single Family",
                "salesStartDate": null,
                "modelOpenDate": null
            }
        ]
    },
    {
        "id": "34F7C7AF-3D1B-4EE7-8271-C99294169C01",
        "name": "College Park / Hillsdale",
        "mktId": 0,
        "status": "Unknown",
        "code": "295D6",
        "ownershipType": null,
        "series": [
            {
                "id": "807144A1-26ED-4657-9775-7DF7563107D3",
                "name": "02",
                "productType": "Detached",
                "productClass": "Single Family",
                "salesStartDate": null,
                "modelOpenDate": null
            }
        ]
    }
]

College Park / Hampshire is duplicated in this example. I need to find the 2 duplicates and return this expected result..

   [
    {
        "id": "66E175A2-A29F-4F1A-AD81-2422B1EB00F6",
        "name": "College Park / Brookhaven",
        "mktId": 0,
        "status": "Unknown",
        "code": "197D6",
        "ownershipType": null,
        "series": [
            {
                "id": "80004F2E-E3C8-4B6A-BCCC-81259AEAF22D",
                "name": "01",
                "productType": "Detached",
                "productClass": "Single Family",
                "salesStartDate": null,
                "modelOpenDate": null
            }
        ]
    },
    {
        "id": "E053E656-4D14-4F2A-AD70-A37F65195CD1",
        "name": "College Park / Hampshire",
        "mktId": 0,
        "status": "Unknown",
        "code": "316D6",
        "ownershipType": null,
        "series": [
            {
                "id": "46830FBD-CD68-4D4C-A095-FB9C3D93D01A",
                "name": "02,03",
                "productType": "Detached",
                "productClass": "Single Family",
                "salesStartDate": null,
                "modelOpenDate": null
            },
            {
                "id": "1BC31692-AAB8-4A00-9D8D-9B8CF7E426E0",
                "name": "01",
                "productType": "Detached",
                "productClass": "Single Family",
                "salesStartDate": null,
                "modelOpenDate": null
            }
        ]
    },
    {
        "id": "34F7C7AF-3D1B-4EE7-8271-C99294169C01",
        "name": "College Park / Hillsdale",
        "mktId": 0,
        "status": "Unknown",
        "code": "295D6",
        "ownershipType": null,
        "series": [
            {
                "id": "807144A1-26ED-4657-9775-7DF7563107D3",
                "name": "02",
                "productType": "Detached",
                "productClass": "Single Family",
                "salesStartDate": null,
                "modelOpenDate": null
            }
        ]
    }
]

vanilla javascript or lodash is fine.

Answer 1

Just set up a hashmap for the ids and a resulting array:

const hash = {}, result = [];

Then iterate over the array:

 for(const el of array){
   const { id, series } = el;

Now we can check if the id already appears in the hash, and if so just add the series:

   if(hash[id]){
     hash[id].series.push(...series);
   } else {

If the id did not appear yet, we need to add the object to our result and to the hashtable:

     result.push(hash[id] = el)
  }
}

And thats already it :)