Count even digits in a number.

countEvenDigits.js

import { modulo, o, not, curry, compose, length, filter, split, map } from 'ramda';

// Number -> Number
const isOdd = o(Boolean, modulo(2));

// Number -> Boolean
const isEven = o(not, isOdd);

// (a -> Boolean) -> [a] -> Number
const countIf = curry(compose(length, filter));

// Number -> [String]
const numberToChars = o(split(''), String);

// Number -> [Number]
const numberToDigits = o(map(Number), numberToChars);

// Number -> Number
const countEvenDigits = o(countIf(isEven), numberToDigits);

export default countEventDigits;

// countEvenDigits(2246221) => 6;