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February 2, 2022

DataWeave Delight: Finding highest or lowest value in an array

DataWeave has several function to find the highest or lowest value in an array. The items in the array need to be of the same type and implement the Comparable interface. To find the highest value we can use the max function. The function returns the maximum value based on the type of the item in the array. If we want to find the highest value based on other criteria we can use the maxBy function. This function takes a lambda as last argument where we can return a Comparable value that is used to determine the highest value. To find the lowest value in an array we have similar functions: min and minBy.

In the following example we use several ways to find the highest and lowest value in arrays with items of different types:


%dw 2.0

// Array with numbers
var numbers = [10, 2, 3, 1, 20]

// Array with string values
var languages = ["DataWeave", "Java", "Groovy", "Clojure"]

// Array with objects representing a user
var users = [
	{ name: "mrhaki", age: 47 },
	{ name: "alice",  age: 32 },
	{ name: "bob",    age: 61 }

output application/json
	// Find maximum for numbers
	maxNumbers: max(numbers),
	// Find minimum for numbers
	minNumbers: min(numbers),
	// Find max for srings looks at first character
	maxLanguages: max(languages),
	// Find min for strings looks at first character
	minLanguages: min(languages),
	// Find language with max length
	maxByLength1: maxBy(languages, (lang) -> sizeOf(lang)),
	// Find max with infix notation
	maxByLength2: languages maxBy (lang) -> sizeOf(lang),
	// Find max with infix notation and $ to reference lambda argument
	maxByLength3: languages maxBy sizeOf($),
	// Find language with minimal length
	minByLength: languages minBy ((lang) -> sizeOf(lang)),
	// Find oldest user with maxBy on objects
	oldestUser: users maxBy ((user) -> user.age),
	// Find youngest user with minBy on objects
	youngestUser: users minBy (user) -> user.age


  "maxNumbers": 20,
  "minNumbers": 1,
  "maxLanguages": "Java",
  "minLanguages": "Clojure",
  "maxByLength1": "DataWeave",
  "maxByLength2": "DataWeave",
  "maxByLength3": "DataWeave",
  "minByLength": "Java",
  "oldestUser": {
    "name": "bob",
    "age": 61
  "youngestUser": {
    "name": "alice",
    "age": 32

Written with DataWeave 2.4.