JSONATA: Creating Array from Nested Array of Objects

Question

I'm new to JSONATA, so this is probably a pretty easy formatting problem that I don't know yet. I need to take a large object and reduce it down into something more manageable. I've been able to do this with objects, but am running into a problem with a particular data structure. It's metadata from a list of images, where the keywords are in an array of objects each with the structure {"name": "keyword"}. Like this:

{
    "body": {
    "files": [
      {
        "id": 101936854,
        "title": "Taco Salad",
        "keywords": [
          {
            "name": "background"
          },
          {
            "name": "baked"
          },
          {
            "name": "beef"
          }
        ]
      },
      {
        "id": 412961542,
        "title": "Fiji",
        "keywords": [
          {
            "name": "beach"
          },
          {
            "name": "sea"
          },
          {
            "name": "tree"
          }
        ]
      }
    ]
  }
}

When I use the query

$zip(body.files.id,body.files.title,body.files.[keywords.name])
{
    "id": $[0],
    "title": $[1],
    "keywords": $[2]
}

I get what I want, but only the first object, like so:

{
  "id": 101936854,
  "title": "Taco Salad",
  "keywords": [
    "background",
    "baked",
    "beef"
  ]
}

If I add the . to output all the objects, I get back multiple objects but only the first value of name in the array. Like so:

$zip(body.files.id,body.files.title,body.files.[keywords.name]).
{
    "id": $[0],
    "title": $[1],
    "keywords": $[2]
}

Gets:

[
  {
    "id": 101936854,
    "title": "Taco Salad",
    "keywords": "background"
  },
  {
    "id": 412961542,
    "title": "Fiji",
    "keywords": "beach"
  }
]

I believe this is because the input objects in that array all have the same key of name. So, I need to somehow get all the values of name and put them in one array called keywords.

mralex · Accepted Answer · 2022-11-24 08:04:53Z

2

If I'm not mistaken, you want something like this:

body.files.{
  "id": id,
  "title": title,
  "keywords": keywords.name
}

or, you can play with the transform operator:

(body ~> |files|{ "keywords": keywords.name }|).files

which produces this output for your example:

[
  {
    "id": 101936854,
    "title": "Taco Salad",
    "keywords": [
      "background",
      "baked",
      "beef"
    ]
  },
  {
    "id": 412961542,
    "title": "Fiji",
    "keywords": [
      "beach",
      "sea",
      "tree"
    ]
  }
]

See it live here https://stedi.link/ybzLADi and here https://stedi.link/TLk7Loq

P.S. if you do want to use $zip for it, I think you'd have to avoid arrays of arrays to prevent JSONata from flattening results, one possible implementation:

$zip(
  body.files.id, 
  body.files.title, 
  body.files.{"keywords": keywords.name}
).{
  "id": $[0], "title": $[1], "keywords": $[2].keywords
}

answered Nov 24, 2022 at 8:04

mralex

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1 Comment

PlanetStarbucks Over a year ago

Excellent, thanks! Indeed, that was a way more streamlined approach to avoid the $zip function. The zip function you provided also worked well, and thanks for providing that. The way that the function treats the inputs makes way more sense with that example, so I learned a good bit from that.

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