eloquent javascript

gistfile1.txt

Треугольник в цикле

for (let i = ''; i.length < 8; i += '#') 
  console.log(i);

FizzBuzz

for (let i = 1; i <= 100; i += 1) {
  switch (true) {
    case i % 3 === 0 && i % 5 === 0:
      console.log('fizz buzz');
      break;
    case i % 3 === 0:
      console.log('fizz');
      break;
  	case i % 5 === 0:
      console.log('buzz');
      break;
    default:
      console.log(i);
  }
}

Шахматная доска

let boardSize = 8;
let desk = ''
let oddRow = true;

for (let i = 1, iEnd = boardSize * boardSize + 1; i < iEnd; i += 1) {
	if (oddRow) desk += i % 2 === 0 ? ' ' : '#';
	else desk += i % 2 === 0 ? '#' : ' ';

  	if (i % boardSize === 0) {
		desk += '\n';
		oddRow = !oddRow;
    }
}

Минимальное из двух

const min = (a, b) => a < b ? a : b;

Рекурсионное isEven:

const isEven = number => {
  const absNumber = Math.abs(number);

  switch(absNumber) {
    case 0: 
      return true;
    case 1: 
      return false;
    case 2:
      return true;
    default: 
     return isEven(absNumber - 2);
  }
}

Подсчет букв в строке

const countBs = string => countChar(string, 'b');
const countChar = (string, char) =>
	string
	.split('')
	.reduce((accum, letter) => letter.toLowerCase() === char ? accum + 1 : accum, 0)
	
Рэндж

const range = (from, to, step = 1) => {
  	const array = [];	
  
	if (step > 0) {
    	for (let i = from; i <= to; i += step)
          array.push(i);
    } else {
    	for (let i = from; i >= to; i += step) 
          array.push(i);
    }
  
  	return array;
}

Сумма элементов массива

const sum = array => array.reduce((sum, number) => sum + number, 0);

Обратный порядок массива не изменяя аргумент

const reverseArray = array => {
  const reversedArray = [];
 
  for (let i = array.length - 1; i >= 0; i -= 1)
  	reversedArray.push(array[i]);     

  return reversedArray;
}

Обратный порядок массива изменяя аргумент

const reverseArrayInPlace = array => {
	for (let i = 0, j = array.length - 1; i < j; i += 1, j -= 1) {
      if (i === j) break;
      
      const temp = array[i];
      array[i] = array[j];
      array[j] = temp;
    }
}

List to array, array to list, порядоковый номер в list

const arrayToList = array => {
  if (array.length === 0) return null;
  
  return { value: array[0], rest: arrayToList(array.slice(1)) }
}

const listToArray = list => {
  if (list.rest === null) return [list.value];
  
  return [ list.value, ...listToArray(list.rest) ]
}

const prepend = (value, rest) => ({ value, rest });

const nth = (list, position, currentPosition = 0) => {
  if (position === currentPosition) return list.value;
  
  return nth(list.rest, position, currentPosition += 1);
};

Flat array

var arrays = [[1, 2, 3], [4, 5], [6]];
console.log(arrays.reduce((accum, item) => accum.concat(item), []))