validations.js

const reduceCompose = (f, g) => x => g(x, f(x))
const reduceComposeArr = (...fns) => fns.reduce(reduceCompose, (x, y) => y)
const isNumber = (x, errors = {}) => Number.isNaN(parseInt(x, 10)) ? Object.assign({}, errors, { number: true }) : errors;
undefined
const length = (z) => (x, errors = {}) => (x && x.length < z) ? Object.assign({}, errors, { length: true }) : errors;
const presence = (x, errors = {}) => x === undefined ? Object.assign({}, errors, { presence: true }) : errors;

reduceComposeArr(presence, length(3), isNumber)('123')