Map an additional key-value in a specific index of a json array using Dataweave 2.0

Question

I have an input payload (json array) that needs to be enriched with a key-value in a specific index. My requirement was to put the additional key-value (the same for all objects) at index 1, so i've managed to do like this:

Input payload:

[
  {
    "key1": "value1",
    "key3": "value3",
    "key4": "value4",
    "key5": "value5"
  },
  {
    "key1": "value1",
    "key3": "value3",
    "key4": "value4",
    "key5": "value5"
  },
  {
    "key1": "value1",
    "key3": "value3",
    "key4": "value4",
    "key5": "value5"
  }
]

Script:

%dw 2.0
output application/json
---
payload map (
        ($)[&0] ++ {"key2": "value2"} ++ ($ - "key1")
    )

Output:

[
  {
    "key1": "value1",
    "key2": "value2",
    "key3": "value3",
    "key4": "value4",
    "key5": "value5"
  },
  {
    "key1": "value1",
    "key2": "value2",
    "key3": "value3",
    "key4": "value4",
    "key5": "value5"
  },
  {
    "key1": "value1",
    "key2": "value2",
    "key3": "value3",
    "key4": "value4",
    "key5": "value5"
  }
]

My question is: how to achieve this dynamically?

Thanks, Marco

Answer 1

Please try the below Script. We declared a variable and added it in each object of your input array. you can declare this vaiable in set variable too basedon requirement if this key value you are getting from payload or from any resource.

%dw 2.0
output application/json
var keyValue = {
    "key2": "value2"
} 
---
payload map ((item, index) -> (item) ++ keyValue ) map ((item1, index) ->(item1) mapObject ((value, key, index) ->((key):value ) ) orderBy ((value, key) ->value ))

Another option where you just need to give a place of index(.g, 2 or 3 or 4 as per equirement) to add key value

%dw 2.0
output application/json
fun addKeyAtPosition(in : Object, position : Number,keyValue : Object)=(
    sizeOf(in) match {
        case size if(position <=0 ) -> (keyValue ++ in)
        case size if(position > size) -> (in ++ keyValue)
        case size if(position <= size) -> (in mapObject ((value, key, index) -> 
 (if ((index+1) == position)
 keyValue ++ ((key): value)
 else ((key): value))
))
else -> keyValue ++ in
    }
)

var keyValue= {
    "key2": "value2"
} 
---
payload map ((item, index) -> 
addKeyAtPosition(item,2,keyValue)        // here we are passing the index as 2
)