lo/docs/data/core-countby.md

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

name	slug	sourceRef	category	subCategory	playUrl	variantHelpers	similarHelpers	position	signatures
CountBy	countby	slice.go#L849	core	slice	https://go.dev/play/p/5GMQP5vNT4q	core#slice#countby	core#slice#count core#slice#every core#slice#some core#slice#filter core#slice#find core#slice#countbyerr	0	func CountBy[T any](collection []T, predicate func(item T) bool) int

Counts the number of elements for which the predicate is true.

lo.CountBy([]int{1, 5, 1}, func(i int) bool {
    return i < 4
})
// 2