countBy

countBy(target, predicate)

Counts the number of elements in the target array satisfy the provided predicate function.

data-first

const isEven = (n) => n % 2 === 0;
countBy([1, 2, 3, 4, 5], isEven); // 2

data-last

const isEven = (n) => n % 2 === 0;
pipe([1, 2, 3, 4, 5], countBy(isEven)); // 2