JSON array group by

json-array-group-by · version 1.0.0 · JSON & JSONL · free, no key needed

Group an array of JSON objects by exact keys.

Use when you need to: json array group by · group json array by keys · bucket json objects.

Supported

• json array group by
• group json array by keys
• bucket json objects

Not supported

• group by expression
• aggregation functions

Behavior

• Groups objects into an array of group records. Each group record has the join keys and a "group" key containing the matching objects.
• Matches objects based on strict equality of the specified keys.
• Output array is ordered by the first appearance of each key tuple.
• The grouped items within each group retain their original relative order.
• Missing or null keys are grouped together and treated as the string 'undefined' or 'null'.

Input

• array (array of object, required): max items 10000
• keys (array of string, required): min items 1; max items 32; each min length 1
• group_name (string, optional): min length 1; max length 64; default "group"

Output

• result (array of object, required)
• groups_count (integer, required)

Limits

• max array items: 10000
• max output items: 10000
• max keys: 32

Example

Request input:

{
  "array": [
    {
      "id": 1,
      "v": "A"
    },
    {
      "id": 2,
      "v": "B"
    },
    {
      "id": 1,
      "v": "C"
    }
  ],
  "keys": [
    "id"
  ]
}

Response:

{
  "result": {
    "result": [
      {
        "id": 1,
        "group": [
          {
            "id": 1,
            "v": "A"
          },
          {
            "id": 1,
            "v": "C"
          }
        ]
      },
      {
        "id": 2,
        "group": [
          {
            "id": 2,
            "v": "B"
          }
        ]
      }
    ],
    "groups_count": 2
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "json-array-group-by",
  "version": "1.0.0",
  "input": {
    "array": [
      {
        "id": 1,
        "v": "A"
      },
      {
        "id": 2,
        "v": "B"
      },
      {
        "id": 1,
        "v": "C"
      }
    ],
    "keys": [
      "id"
    ]
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/json-array-group-by/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"array":[{"id":1,"v":"A"},{"id":2,"v":"B"},{"id":1,"v":"C"}],"keys":["id"]}'

The machine-readable contract is at /v1/tools/json-array-group-by/versions/1.0.0.

CLI

node cli.mjs run json-array-group-by 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• JSON array group count: Group an array of JSON objects by exact keys and return the count.
• JSON array sort objects: Stably sort an array of objects by explicit string keys using UTF-16 lexicographic order.
• JSON array anti join: Anti join two JSON arrays of objects on exact keys.
• JSON array distinct by: Deduplicate a JSON array of objects based on specific keys.
• JSON array filter equals: Filter JSON array objects where a key equals a specific value.
• JSON array inner join: Inner join two JSON arrays of objects on exact keys.