Beraliv

function digitAt(index, amount) {
  if (index <= 0) {
    throw new TypeError('index must be positive')
  }
  return Math.floor(amount * Math.pow(10, index) % 10)
}

function restAfter(index, amount) {
  const indent = Math.pow(10, index)
  const rest = amount * indent % indent

Beraliv

// it can be optimised via lazy evaluation or cached values
function factorial(n) {
  if (n < 0) {
    throw new TypeError('n should be non-negative')
  }
  if (n < 2) {
    return 1
  }
  return n * factorial(n - 1)
}

Beraliv

const digitalRoot = n => {
  return Math.abs((n - 1) % 9 + 1)
}

console.log(digitalRoot(1)) // should be 1
console.log(digitalRoot(11)) // should be 2
console.log(digitalRoot(19)) // should be 1
console.log(digitalRoot(191)) // should be 2
console.log(digitalRoot(1918)) // should be 1
console.log(digitalRoot(65536)) // should be 7

Beraliv

const permutation = (arr) => {
  let max
  const set = []

  // set maximum and set
  for (let i = 0; i < arr.length; i++) {
    const element = arr[i]
    // update maximum of elements
    if (!max || max < element) {
      max = element

Beraliv

const fact = n => n < 1
  ? 1
  : Array(n)
    .fill(0)
    .map((_, i) => i + 1)
    .reduce((a, v) => a * v, 1);

const countOf5 = n => Math.floor((n + 5) / 10);
const countOf10 = n => Math.floor(n / 10);

Beraliv

/*
 *  It's not technically correct as there are possible numbers
 *  that have more than one subsequence of exact digits: 7774777
 *  but here it's considered only one possible subsequence of exact digits
 */
const answer = n => {
  const allPossibleCount = n === 0 ? 0 : Math.pow(2, n);
  const threeOrMoreSameDigitInARowCount = Array(Math.max(n - (3 + index) + 1, 0))
    .fill(0)
    .map((_, index) => (n - 3 + index) * 2)

Beraliv

const g = n => {
  const array = Array.from(Array(n), (_, i) => i + 1);
  const indices = Array.from(Array(n + 1), (_, i) => i);

  const returnF = k => {
    const types = array.slice(k).map(t => `T${t}`);
    return types.length === 0 
      ? 'R' 
      : `CurriedFunction${n - k}<${types.join(', ')}, R>`;
  }

Beraliv

const g = n => {
  const array = Array.from(Array(n), (_, i) => i + 1);
  const indices = Array.from(Array(n + 1), (_, i) => i);

  const returnF = k => {
    const types = array.slice(k).map(t => `T${t}`);
    return types.length === 0 
      ? 'R' 
      : `CurriedFunction${n - k}<${types.join(', ')}, R>`;
  }

Beraliv

// https://raw.githubusercontent.com/donnut/typescript-ramda/master/ramda.d.ts
// https://raw.githubusercontent.com/DefinitelyTyped/DefinitelyTyped/master/lodash/lodash.d.ts

declare namespace fp {

	interface Dictionary<T> {
		[index: string]: T;
	}

	interface CurriedFunction1<T1, R> {

Beraliv

const BigInteger = value => {
  const normalise = n => {
    if ((n | 0) === 0) {
      return '0';
    }

    n = n.toString().split('');

    while (+n[0] === 0) {
      n.splice(0, 1);