Add serial number to JSON

Question

I've a JSON:

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

I want to add additional key called order_id to all objects in this json and set value as objects order in json (serial number). First object in json should have order_id = 1, etc.... Amount of objects in json can be different, it's just example.

I expect this json: Expected result:

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

Answer 1

You can use two stages of transformations such as

[ // replicate each objects' index within the array
  //(they always start from 0 and increments by 1)
  {
    "operation": "shift",
    "spec": {
      "*": {
        "*": "[#2].&", // replicate all existing attributes
        "$": "[#2].order_id"
      }
    }
  },
  { // increment each of those indexes by 1
    "operation": "modify-overwrite-beta",
    "spec": {
      "*": {
        "order_id": "=intSum(1,@(1,&))"
      }
    }
  },
  { // sort by attributes' names
    "operation": "sort"
  }
]

the demo on the site http://jolt-demo.appspot.com/ is :