lo/docs/data/core-countvaluesby.md

name, slug, sourceRef, category, subCategory, playUrl, variantHelpers, similarHelpers, position, signatures

name	slug	sourceRef	category	subCategory	playUrl	variantHelpers	similarHelpers	position	signatures
CountValuesBy	countvaluesby	slice.go#L623	core	slice	https://go.dev/play/p/2U0dG1SnOmS	core#slice#countvaluesby	core#slice#countvalues core#slice#groupby core#slice#map core#slice#mapvalues	0	func CountValuesBy[T any, U comparable](collection []T, mapper func(item T) U) map[U]int

Counts the number of each mapped value (equivalent to Map followed by CountValues).

isEven := func(v int) bool {
    return v%2 == 0
}
lo.CountValuesBy([]int{1, 2, 2}, isEven)
// map[bool]int{false: 1, true: 2}