Merging Array of Objects with same key

Question

I have an array as under

Data =

 [
  {
    "field": "Classifications.LEV_2_HIER_NME",
    "value": "Treasury Note",
    "aggregates": {
      "VALVAL_ALT_CMB_AMT": {
        "sum": "5,981,210,920.0000"
      }
    },
    "Items": [
      {
        "field": "Classifications.LEV_1_HIER_NME",
        "value": "Treasury 1",
        "aggregates": {
          "VALVAL_ALT_CMB_AMT": {
            "sum": "5,981,210,920.0000"
          }
        },
        "Items": []
      },
      {
        "field": "Classifications.LEV_1_HIER_NME",
        "value": "Treasure 1",
        "aggregates": {
          "VALVAL_ALT_CMB_AMT": {
            "sum": "5,981,210,920.0000"
          }
        },
        "Items": []
      }
    ]
  },
  {
    "field": "Classifications.LEV_2_HIER_NME",
    "value": "Treasury Note",
    "aggregates": {
      "VALVAL_ALT_CMB_AMT": {
        "sum": "8,981,210,920.0000"
      }
    },
    "Items": [
      {
        "field": "Classifications.LEV_1_HIER_NME",
        "value": "Treasury 1",
        "aggregates": {
          "VALVAL_ALT_CMB_AMT": {
            "sum": "8,981,210,920.0000"
          }
        },
        "Items": []
      },
      {
        "field": "Classifications.LEV_1_HIER_NME",
        "value": "Treasure 1",
        "aggregates": {
          "VALVAL_ALT_CMB_AMT": {
            "sum": "8,981,210,920.0000"
          }
        },
        "Items": []
      }
    ]
  }
]

Data array has two objects. I want to merge the aggregate property of second object in the first one.

something like this:

[
  {
    "field": "Classifications.LEV_2_HIER_NME",
    "value": "Treasury Note",
    "aggregates": {
      "VALVAL_ALT_CMB_AMT": {
        "sum": "5,981,210,920.0000"
      },
      "VALVAL_ALT_CMB_AMT_1": {
        "sum": "8,981,210,920.0000"
      }
    },
    "Items": [
      {
        "field": "Classifications.LEV_1_HIER_NME",
        "value": "Treasury 1",
        "aggregates": {
          "VALVAL_ALT_CMB_AMT": {
            "sum": "5,981,210,920.0000"
          },
          "VALVAL_ALT_CMB_AMT_1": {
            "sum": "8,981,210,920.0000"
          }
        },
        "Items": []
      },
      {
        "field": "Classifications.LEV_1_HIER_NME",
        "value": "Treasure 1",
        "aggregates": {
          "VALVAL_ALT_CMB_AMT": {
            "sum": "5,981,210,920.0000"
          },
          "VALVAL_ALT_CMB_AMT_1": {
            "sum": "8,981,210,920.0000"
          }
        },
        "Items": []
      }
    ]
  }
]

is there any way to implement this. Level of nesting is dynamic but all the objects will have same structure.

"is there any way to implement this" - yes, but it would be better to share your attempt as a minimal reproducible example. Then we can help with where you're stuck. — evolutionxbox
– evolutionxbox, Commented Sep 1, 2021 at 15:24
@Andreas it could be, but the DATA = at the beginning makes me think not... — evolutionxbox
– evolutionxbox, Commented Sep 1, 2021 at 15:28
Please also note that the aggregates property name is misspelled, which you might want to fix depending on where you receive this data from — Jotha
– Jotha, Commented Sep 1, 2021 at 15:30

Prashin Jeevaganth · Accepted Answer · 2021-09-02 00:45:25Z

1

To merge the 2 objects inside the array into 1, this involves

Step 1. extracting the required elements from the 2nd object

Step 2. adding it into the object of the first.

Suppose the array is read into a variable data, then this is 1 way we can extract it in Step 1.

let {
  aggregates: {
      VALVAL_ALT_CMB_AMT
  },
} = data[1];

The value paired to the VALVAL_ALT_CMB_AMT key of the 2nd object is stored inside a variable VALVAL_ALT_CMB_AMT. You can read more about Object Destructuring in Javascript.

For Step 2, we will add the value into the first variable. We can also think of objects to have similar syntax to maps, hence this is 1 way we can do it.

let first = data[0];
first["aggregates"]["VALVAL_ALT_CMB_AMT_1"] = VALVAL_ALT_CMB_AMT;

Extracting and adding the elements this way forms a shallow copy of the variable VALVAL_ALT_CMB_AMT, now as a value of VALVAL_ALT_CMB_AMT_1. Consequently, it is not advisable to delete the actual object in position 1 from the original array. Instead, it might be better to return the new object first in a new array.

const result = [first];
return result;

answered Sep 2, 2021 at 0:45

Prashin Jeevaganth

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9 Comments

Amit Over a year ago

Hi Prashin . Thanks for the solution. I am trying to implement the same but facing difficulty as nested level is dynamic.

Prashin Jeevaganth Over a year ago

Could you elaborate or maybe add an example to illustrate the "dynamic" restriction?

Amit Over a year ago

Hi Prashin . Thanks for the solution. I am trying to implement the same but facing difficulty as nested level is dynamic. stackblitz.com/edit/… in data-modifier.service.ts I am trying to achieve the same. Although I am able to get to the lowest level of nesting but not able to update the same level for [first]

Amit Over a year ago

stackblitz.com/edit/…

Prashin Jeevaganth Over a year ago

@Amit I still don't quite get what you mean, and I don't know how your application works too. Do you have a rather complicated nesting example that you would like to merge? Maybe you can also provide that expected output.

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