如何在 Node.js 中过滤这个 object 数组？

Question

I have some data which looks like this-

[
   {
      "element": 1,
      "id": 1
   },
   {
      "element": 1,
      "id": 2
   },
   {
      "element": 2,
      "id": 1
   },
   {
      "element": 2,
      "id": 2
   },
   {
      "element": 3,
      "id": 1
   }
]

I have data as above as it is array of object and I want to filter as given below mainly in Node.js where I want to filter with element and return new array. It will be helpful if I get any solution for this.

[
   {
      "element": 1,
      "data": [
         {
            "element": 1,
            "id": 1
         },
         {
            "element": 1,
            "id": 2
         }
      ]
   },
   {
      "element": 2,
      "data": [
         {
            "element": 2,
            "id": 1
         }
      ]
   },
   {
      "element": 3,
      "data": [
         {
            "element": 3,
            "id": 1
         }
      ]
   }
]

Answer 1

Okay, so let's get some variables in:

const elementsData = [{ element: 0001, id: 1 }, { element: 0001, id: 2 }, { element: 0001, id: 3 }, { element: 0001, id: 4 }, { element: 0002, id: 1 }, { element: 0002, id: 2 }, { element: 0002, id: 3 }, { element: 0003, id: 1 } ]

First, You'll need to filter out the unique element values:

const uniqueElements = []
elementsData.forEach(datum => {
   if (!uniqueElements.includes(datum.element)) {
      uniqueElements.push(datum.element)
   }
})

Then do groupings by uniqueElement

// loop through the unique Elements
const output = uniqueElements.map(uniqueElement => {
   // this will return the object with the specified fields
   return {
       // element value
       element: uniqueElement,

       // filter through elementsData for matching elements and save then into an array.
       // You can do sort() here if you want to sort them by id, but this is basically it
       data: elementsData.filter(elementData => elementsData.element === uniqueElement)
   }
})