Mulesoft – Merge two arrays by Identifier in dataweave

Use Case: When we have two arrays in different mule variables (or one in payload and one in variable), merge two arrays into a single array. We can use below dataweave logic to merge by an identifier.

Input:
Payload:
{
    "orders": [
        {
            "id": 123,
            "customer": "c1"
        },
        {
            "id": 124,
            "customer": "c2"
        }
    ]
}

orderVar:
{
    "orders": [
        {
            "id": 123,
            "number": "xyz1"
        },
        {
            "id": 124,
            "number": "xyz2"
        }
    ]
}

Dataweave:
%dw 2.0
output application/json
---
"orders":payload.orders map (record,index) -> {
    (vars.orderVar.orders filter (record.id == $.id) map (record2,index2) -> {
        "id": record.id,
        "number": record2.number,
        "customer": record.customer
    })
}

Output:
{
  "orders": [
    {
      "id": 123,
      "number": "xyz1",
      "customer": "c1"
    },
    {
      "id": 124,
      "number": "xyz2",
      "customer": "c2"
    }
  ]
}

In few scenarios we might need to merge by index of both input and output. Example, for salesforce bulk update/creates the response will be in the same order of the request payload. Here we should use index as an identifier. Below is the sample code.

%dw 2.0
output application/json
---
"orders":payload.orders map (record,index) -> {
    (vars.orderVar.orders filter ($$ == index) map (record2,index2) -> {
        "id": record.id,
        "number": record2.number,
        "customer": record.customer
    })
}