MuleSoft Dataweave reduce

Question

I try to get my head around the reduce function in Mulesoft Dataweave 2.0.

expected outcome:

{
  "dev": "1",
  "test": "2",
  "uat": "3",
  "prod": "4"
}

my dataweave code:

%dw 2.0
var invar = [
  {"id": "1", "name": "dev"},
  {"id": "2", "name": "test"},
  {"id": "3", "name": "uat"},
  {"id": "4", "name": "prod"}
]
output application/json
---
// invar reduce() ???  requirment: it must be done with reduce function.

Thanks

Answer 1

The trick is to set the accumulator to the correct value when DataWeave can not deduce it automatically:

%dw 2.0
var invar = [
  {"id": "1", "name": "dev"},
  {"id": "2", "name": "test"},
  {"id": "3", "name": "uat"},
  {"id": "4", "name": "prod"}
]
output application/json
---
invar reduce ((item, accumulator= {}) -> accumulator ++ {(item.name):item.id})

Answer 2

Initialise accumulator to empty object {} and add the formed key value pairs to the accumulator for the required output:

invar reduce ((item, accumulator = {}) -> accumulator ++ {(item.name): item.id } )