Define a Custom Addition Function
This DataWeave example takes in a set of item prices and stock amounts and uses several functions to calculate subtotals, deduct discounts and add taxes.
It makes use of the following:
-
mapfunction to go through all the items in the input. -
basic math operations like
*,+and-. -
String concatenation with
++. -
asto force string values into numbers. -
Fixed values in the header to set tax and discount amounts.
-
A custom function in the header, to define once and use multiple times in the code.
-
reducefunction to aggregate the various items into a total.
DataWeave Script:
%dw 2.0
output application/json
var tax = 0.085
var discount = 0.05
fun getSubtotal (items) = items reduce ((item, accumulator = 0) ->
accumulator + (item.unit_price * item.quantity * (1 - discount)))
---
invoice: {
header: payload.invoice.header,
items: { (payload.invoice.items map {
item : {
description: $.description,
quantity: $.quantity,
unit_price: $.unit_price,
discount: (discount * 100) as Number ++ "%",
subtotal: $.unit_price * $.quantity * (1 - discount)
}
}) },
totals:
{
subtotal: getSubtotal(payload.invoice.items ),
tax: (tax * 100) as Number ++ "%",
total: getSubtotal(payload.invoice.items ) * (1 + tax)
}
}Input JSON Payload:
{
"invoice": {
"header": {
"customer_name": "ACME, Inc.",
"customer_state": "CA"
},
"items": [
{
"description": "Product 1",
"quantity": "2",
"unit_price": "10"
},
{
"description": "Product 2",
"quantity": "1",
"unit_price": "30"
}
]
}
}Output
{
"invoice": {
"header": {
"customer_name": "ACME, Inc.",
"customer_state": "CA"
},
"items": {
"item": {
"description": "Product 1",
"quantity": "2",
"unit_price": "10",
"discount": "5%",
"subtotal": 19.00
},
"item": {
"description": "Product 2",
"quantity": "1",
"unit_price": "30",
"discount": "5%",
"subtotal": 28.50
}
},
"totals": {
"subtotal": 47.50,
"tax": "8.500%",
"total": 51.53750
}
}
}