Extract field from mongodb query result set-CodePudding

How to extract json field from query response in node js?

I have a query:-

const Allposts = await Post.aggregate([pipeline])

Allposts:-

  {
    _id: 1,
    type: 'A',
    source: 'B',
    status: 'C',
    totalCount: 7,
    createdAt: 2022-04-13T17:12:28.097Z,
    updatedAt: 2022-04-13T17:12:28.097Z,
    __v: 0
  },
 {
    _id: 2,
    type: 'A',
    source: 'B',
    status: 'C',
    totalCount: 7,
    createdAt: 2022-04-13T17:12:28.097Z,
    updatedAt: 2022-04-13T17:12:28.097Z,
    __v: 0
  },
 {
    _id: 3,
    type: 'A',
    source: 'B',
    status: 'C',
    totalCount: 7,
    createdAt: 2022-04-13T17:12:28.097Z,
    updatedAt: 2022-04-13T17:12:28.097Z,
    __v: 0
  }, and so on

I want to extract the totalCount field and store its value how to do this?

CodePudding user response：

Assuming totalCount value will be same in all the objects, you can extract the first value using first index

let tc = Allposts[0].totalCount;

let data = [{
    _id: 1,
    type: 'A',
    source: 'B',
    status: 'C',
    totalCount: 7,
    createdAt: '2022 - 04 - 13 T17: 12: 28.097 Z',
    updatedAt: '2022 - 04 - 13 T17: 12: 28.097 Z',
    __v: 0
  },
  {
    _id: 2,
    type: 'A',
    source: 'B',
    status: 'C',
    totalCount: 7,
    createdAt: '2022 - 04 - 13 T17: 12: 28.097 Z',
    updatedAt: '2022 - 04 - 13 T17: 12: 28.097 Z',
    __v: 0
  },
  {
    _id: 3,
    type: 'A',
    source: 'B',
    status: 'C',
    totalCount: 7,
    createdAt: '2022 - 04 - 13 T17: 12: 28.097 Z',
    updatedAt: '2022 - 04 - 13 T17: 12: 28.097 Z',
    __v: 0
  }
]

let tc = data[0].totalCount;

console.log(tc);

CodePudding user response：

If you get only totalCount field from query response, you can add .project() in query as below

const Allposts = await Post.aggregate().project("totalCount -_id");