countBy

countBy<T>(array: Array<T>, matchingFunction: (T) -> Boolean): Number

Counts the elements in an array that return true when the matching function is applied to the value of each element.

Parameters

Name Description

Name	Description
`array`	The input array that contains elements to match.
`matchingFunction`	A function to apply to elements in the input array.

array

The input array that contains elements to match.

matchingFunction

A function to apply to elements in the input array.

Example

This example counts the number of elements in the input array ([1, 2, 3, 4]) that return true when the function (($ mod 2) == 0) is applied their values. In this case, the values of two of the elements, both 2 and 4, match because 2 mod 2 == 0 and 4 mod 2 == 0. As a consequence, the countBy function returns 2. Note that mod returns the modulus of the operands.

Source

%dw 2.0
import * from dw::core::Arrays
output application/json
---
{ "countBy" : [1, 2, 3, 4] countBy (($ mod 2) == 0) }

Output

{ "countBy": 2 }

countBy(array: Null, matchingFunction: (Nothing) -> Any): Null

Helper function that enables countBy to work with a null value.

Introduced in DataWeave version 2.4.0.