JSON array anti join

json-array-anti-join · version 1.0.0 · JSON & JSONL · free, no key needed

Anti join two JSON arrays of objects on exact keys.

Use when you need to: json array anti join · anti join json arrays · subtract json arrays by keys.

Supported

json array anti join
anti join json arrays
subtract json arrays by keys

Not supported

fuzzy keys
numeric keys within arrays

Behavior

Matches objects from the left and right arrays based on strict equality of the specified keys.
Returns a new array containing only the left rows that have NO match in the right array.
Output array is ordered by the left array's order.
If a left row is missing any of the join keys, it is treated as having no match, so it is ALWAYS included in the output.
If a right row is missing any of the join keys, it never matches any left row.

Input

left (array of object, required): max items 10000
right (array of object, required): max items 10000
keys (array of string, required): min items 1; max items 32; each min length 1

Output

result (array of object, required)
count (integer, required)

Limits

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

Example

Request input:

{
  "left": [
    {
      "id": 1,
      "name": "Alice"
    },
    {
      "id": 2,
      "name": "Bob"
    }
  ],
  "right": [
    {
      "id": 1,
      "role": "Admin"
    }
  ],
  "keys": [
    "id"
  ]
}

Response:

{
  "result": {
    "result": [
      {
        "id": 2,
        "name": "Bob"
      }
    ],
    "count": 1
  }
}

How to call it

MCP

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

{
  "id": "json-array-anti-join",
  "version": "1.0.0",
  "input": {
    "left": [
      {
        "id": 1,
        "name": "Alice"
      },
      {
        "id": 2,
        "name": "Bob"
      }
    ],
    "right": [
      {
        "id": 1,
        "role": "Admin"
      }
    ],
    "keys": [
      "id"
    ]
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/json-array-anti-join/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"left":[{"id":1,"name":"Alice"},{"id":2,"name":"Bob"}],"right":[{"id":1,"role":"Admin"}],"keys":["id"]}'

The machine-readable contract is at /v1/tools/json-array-anti-join/versions/1.0.0.

CLI

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

Get the client at /clients/cli/.

JSON array inner join: Inner join two JSON arrays of objects on exact keys.
JSON array left join: Left join two JSON arrays of objects on exact keys.
JSON array group by: Group an array of JSON objects by exact keys.
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 concat: Concatenate multiple JSON arrays of objects into one.