Sharing one from my day-to-day tasks along with the approach I used to complete it.

I am given a file with an array of old records. The array is structured as follows:

Let us call it - input.json

[
  {
    "myId": "parent-1",
    "parentOwnFields": {},
    "childIds": [
      {
        "childId": "child-a-1",
        "childName": "child-a-1"
      },
      {
        "childId": "child-b-1",
        "childName": "child-b-1"
      }
    ]
  },
  {
    "myId": "child-a-1",
    "childAFields": {}
  },
  {
    "myId": "child-b-1",
    "childBFields": {}
  },
  {
    "myId": "parent-2",
    "parentOwnFields": {},
    "childIds": [
      {
        "childId": "child-a-2",
        "childName": "child-a-2"
      },
      {
        "childId": "child-b-2",
        "childName": "child-b-2"
      }
    ]
  },
  {
    "myId": "child-a-2",
    "childAFields": {}
  },
  {
    "myId": "child-b-2",
    "childBFields": {}
  }
]

Task:

Using input.json, I have to build another array of objects that follows the below structure: (basically to combine parent item with its child items)

[
  {
    "myId": "child-b-1",
    "parentOwnFields": {},
    "childIds": [
      {
        "childId": "child-a-1",
        "childName": "child-a-1"
      },
      {
        "childId": "child-b-1",
        "childName": "child-b-1"
      }
    ],
    "childAFields": {},
    "childBFields": {}
  },
  {
    "myId": "child-b-2",
    "parentOwnFields": {},
    "childIds": [
      {
        "childId": "child-a-2",
        "childName": "child-a-2"
      },
      {
        "childId": "child-b-2",
        "childName": "child-b-2"
      }
    ],
    "childAFields": {},
    "childBFields": {}
  }
]

My Approach:

• Declared & initialized 3 empty arrays - parentItems, childItems,result

let parentItems = []
let childItems = []
let result = []

• Getting all parent items in parentItems array.

• Getting all child items in childItems array.

for (const item of oldRecords) {
    if (!!item?.childIds) {
        parentItems.push(item)
    } else {
        childItems.push(item)
    }
}

In iteration, to identify if item is parent or not, I used childIds (like a flag).

If item has childIds field, it is a parent item otherwise child item.

• Looping over parentItems array.

• For each parentItem, again looping over its childIds, to collect its 2 child items from childItems array using array's find method.

for (let parentItem of parentItems) {
    for (const childItem of parentItem.childIds) {
        let foundChildItem = childItems.find(child => child.myId === childItem.childId)
        if (foundChildItem) {
            parentItem = { ...parentItem, ...foundChildItem }
        }
    }
    result.push(parentItem)
}

• Merging a parent item with its 2 child items. Pushing it to result array.

code-file

If I could have done it with a different approach, your points are welcome in the comments.

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Thank you for reading my write-up. 📝💻

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