csvToJson.dwl

%dw 2.0
input payload csv
output application/json
var category = (age: Number) -> if (age < 30) "young" else "adult"
---
payload map (row, rowIndex) -> {
    name: row.name,
    age: row.age as Number,
    city: row.city,
    category: category(row.age)
}

input.csv

output.json

[
    {
        "name": "John",
        "age": 30,
        "city": "New York",
        "category": "adult"
    },
    {
        "name": "Jane",
        "age": 25,
        "city": "Los Angeles",
        "category": "young"
    }
]