Adding a new JSON key from an existing JSON value-CodePudding

I have the following JSON;

[
  {
    "id": 1,
    "start": "2022-06-20",
    "result": 24
  },
  {
    "id": 2,
    "start": "2022-06-21",
    "result": 56
  },
  {
    "id": 3,
    "start": "2022-06-21",
    "result": 78
  }
]

I'm wanting to add 2 new values to each array above using JQ, dimension and date, but date needs to be a copy of the existing key value start. The expected output is as below;

[
  {
    "id": 1,
    "start": "2022-06-20",
    "result": 24,
    "date": "2022-06-20",
    "dimension": "new"
  },
  {
    "id": 2,
    "start": "2022-06-21",
    "result": 56,
    "date": "2022-06-21",
    "dimension": "new"
  },
  {
    "id": 3,
    "start": "2022-06-21",
    "result": 78,
    "date": "2022-06-21",
    "dimension": "new"
  }
]

The jq I have at present can add the new key dimension, but I can't figure out how to copy start -> date

jq '.[]  = {"dimension": "new"}' input.json

Thanks for any help

CodePudding user response：

Just create the new key / value pairs.

jq 'map(.date = .start | .dimension = "new")' input.json

CodePudding user response：

You might have tried the following:

.[]  = { date: .start, dimension: "new" }    // WRONG

But it's not quite right since . is the array, not the element of the array. You can use |= as a topicalizer.

.[] |= ( .  = { date: .start, dimension: "new" } )

But I'd use map instead.

map( .  = { date: .start, dimension: "new" } )

Alternatively,

.  = { date: .start, dimension: "new" }

can also also be achieved using

.date = .start | .dimension: "new"

So you could use

.[] |= ( .date = .start | .dimension: "new" )

map( .date = .start | .dimension = "new" )