Kohei Matsubara matsuby

## isLeapYear.js
// =================================================================
// https://en.wikipedia.org/wiki/Proleptic_Gregorian_calendar
// =================================================================

// for ES2015
{
  const isLeapYear = y => !!(+y===parseInt(y)&&!y.pop&&(y%4)^(y%100)|!(y%400));

  const testParams = [
    // expect: true  (is leap)

## parseQuery_buildQuery.js
// for ES2017
{
  // "name=matsuby&age=27" => {name: "matsuby", age: "27"}
  const parseQuery = qs => typeof qs!=="string"?{}:Object.assign({},...Object.entries([...new URLSearchParams(qs)].reduce((a,c)=>Object.assign(a,{[c[0]]:a[c[0]]?[...a[c[0]],c[1]]:[c[1]]}),{})).map(e=>({[e[0]]:e[1].join(",")})));

  // {name: "matsuby", age: "27"} => "name=matsuby&age=27"
  const buildQuery = qo => new URLSearchParams(Object.entries(qo).map(kv=>kv[1].split(",").map(v=>[kv[0],v])).reduce((a,c)=>a.concat(c),[])).toString();


  const testParams = [

## groupArr2d_groupConcatArr2d.js
// for ES2017
{
  const groupArr2d = (arr2d, {swap=false} = {}) => arr2d.reduce((a,c)=>Object.assign(a,{[c[+swap]]:a[c[+swap]]?[...a[c[+swap]],c[+!swap]]:[c[+!swap]]}),{});

  const groupConcatArr2d = (arr2d, {swap=false, glue=","} = {}) => Object.assign({},...Object.entries(arr2d.reduce((a,c)=>Object.assign(a,{[c[+swap]]:a[c[+swap]]?[...a[c[+swap]],c[+!swap]]:[c[+!swap]]}),{})).map(e=>({[e[0]]:e[1].join(glue)})));

  // two-dimensional arrays can represent object.
  // in each array, the first value can be regarded as a key, and the next value can be regarded as a value.
  // `Object.entries(obj)` is easy to understand as an example.
  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries#Examples

## fibonacci.js
// =========================================================================
// https://en.wikipedia.org/wiki/Fibonacci_number#List_of_Fibonacci_numbers
// =========================================================================

// for ES2015
{
  const fibonacci = Object.assign(function f(n){return +n!==parseInt(n)||!isFinite(n)?NaN:Math.abs(n)>1476?Math.sign(n)*Infinity:(n>=0?1:~n%2?-1:1)*(f[Math.abs(n)]||(f[Math.abs(n)-1]=f(Math.abs(n)-1))+f[Math.abs(n)-2])},{"-2":-1,"-1":1,0:0,1:1});


  const positiveIntegers = [...[...Array(21).keys()], 100, 999, 1476, 1477, 1478, 1479];

## index.html
<!doctype html>
<html lang="ja">
<head>
  <meta charset="utf-8">
  <title>d3を使って円から円を直線で結ぶサンプル</title>
</head>
<body>
  <div id="container"></div>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/5.7.0/d3.min.js"></script>
  <script>

## calcPieChartValues.js
{
  const calcPieChartValues = (values, numDegits = null) => {
    const totalValue = values.reduce((a, c) => a + c);
    const deg2rad = (deg) => deg * Math.PI / 180;

    return values.map((value, i) => {
      const data = {};
      data.index     = i;
      data.value     = value;
      data.rate      = value / totalValue;

## combinations.ts
/**
 * Returns an array of all combinations of elements from all arrays.
 *
 * @examples
 *   combinations([1], [2, 3], [4, 5, 6])
 *   => "[[1,2,4],[1,2,5],[1,2,6],[1,3,4],[1,3,5],[1,3,6]]"
 */
export const combinations = <T extends unknown>(...arrays: T[][]): T[] => {
  const result: T[] = []
  const _combinations = (n: number, current: T[]) => {

## sumObjects.ts
/**
 * sumObjects([
 *   {a: 1, b: 2},
 *   {b: 3, c: 4},
 * ])
 * => {a: 1, b: 5, c: 4}
 */
const sumObjects = (
  objects: Record<string, number>[]
): Record<string, number> =>

## cumulativeSumObjects.ts
/**
 * cumulativeSumObjects({
 *   20200101: {a: 1, b: 2, c: 3},
 *   20200102: {b: 1, c: 2, d: 3},
 *   20200103: {c: 1, d: 2, e: 3},
 * })
 * => {
 *   20200101: {a: 1, b: 2, c: 3, d: 0, e: 0},
 *   20200102: {a: 1, b: 3, c: 5, d: 3, e: 0},
 *   20200103: {a: 1, b: 3, c: 6, d: 5, e: 3},

## useStep.ts
import { useState } from 'react'

export const useStep = <
  T extends {
    [step: string]: string
  }
>({
  steps,
  initialStep,
}: {
	// =================================================================
	// https://en.wikipedia.org/wiki/Proleptic_Gregorian_calendar
	// =================================================================

	// for ES2015
	{
	const isLeapYear = y => !!(+y===parseInt(y)&&!y.pop&&(y%4)^(y%100)\|!(y%400));

	const testParams = [
	// expect: true (is leap)
	// for ES2017
	{
	// "name=matsuby&age=27" => {name: "matsuby", age: "27"}
	const parseQuery = qs => typeof qs!=="string"?{}:Object.assign({},...Object.entries([...new URLSearchParams(qs)].reduce((a,c)=>Object.assign(a,{[c[0]]:a[c[0]]?[...a[c[0]],c[1]]:[c[1]]}),{})).map(e=>({[e[0]]:e[1].join(",")})));

	// {name: "matsuby", age: "27"} => "name=matsuby&age=27"
	const buildQuery = qo => new URLSearchParams(Object.entries(qo).map(kv=>kv[1].split(",").map(v=>[kv[0],v])).reduce((a,c)=>a.concat(c),[])).toString();


	const testParams = [
	// for ES2017
	{
	const groupArr2d = (arr2d, {swap=false} = {}) => arr2d.reduce((a,c)=>Object.assign(a,{[c[+swap]]:a[c[+swap]]?[...a[c[+swap]],c[+!swap]]:[c[+!swap]]}),{});

	const groupConcatArr2d = (arr2d, {swap=false, glue=","} = {}) => Object.assign({},...Object.entries(arr2d.reduce((a,c)=>Object.assign(a,{[c[+swap]]:a[c[+swap]]?[...a[c[+swap]],c[+!swap]]:[c[+!swap]]}),{})).map(e=>({[e[0]]:e[1].join(glue)})));

	// two-dimensional arrays can represent object.
	// in each array, the first value can be regarded as a key, and the next value can be regarded as a value.
	// `Object.entries(obj)` is easy to understand as an example.
	// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries#Examples
	// =========================================================================
	// https://en.wikipedia.org/wiki/Fibonacci_number#List_of_Fibonacci_numbers
	// =========================================================================

	// for ES2015
	{
	const fibonacci = Object.assign(function f(n){return +n!==parseInt(n)\|\|!isFinite(n)?NaN:Math.abs(n)>1476?Math.sign(n)Infinity:(n>=0?1:~n%2?-1:1)(f[Math.abs(n)]\|\|(f[Math.abs(n)-1]=f(Math.abs(n)-1))+f[Math.abs(n)-2])},{"-2":-1,"-1":1,0:0,1:1});


	const positiveIntegers = [...[...Array(21).keys()], 100, 999, 1476, 1477, 1478, 1479];
	<!doctype html>
	<html lang="ja">
	<head>
	<meta charset="utf-8">
	<title>d3を使って円から円を直線で結ぶサンプル</title>
	</head>
	<body>
	<div id="container"></div>
	<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/5.7.0/d3.min.js"></script>
	<script>
	{
	const calcPieChartValues = (values, numDegits = null) => {
	const totalValue = values.reduce((a, c) => a + c);
	const deg2rad = (deg) => deg * Math.PI / 180;

	return values.map((value, i) => {
	const data = {};
	data.index = i;
	data.value = value;
	data.rate = value / totalValue;
	/**
	* Returns an array of all combinations of elements from all arrays.
	*
	* @examples
	* combinations([1], [2, 3], [4, 5, 6])
	* => "[[1,2,4],[1,2,5],[1,2,6],[1,3,4],[1,3,5],[1,3,6]]"
	*/
	export const combinations = <T extends unknown>(...arrays: T[][]): T[] => {
	const result: T[] = []
	const _combinations = (n: number, current: T[]) => {
	/**
	* sumObjects([
	* {a: 1, b: 2},
	* {b: 3, c: 4},
	* ])
	* => {a: 1, b: 5, c: 4}
	*/
	const sumObjects = (
	objects: Record<string, number>[]
	): Record<string, number> =>
	/**
	* cumulativeSumObjects({
	* 20200101: {a: 1, b: 2, c: 3},
	* 20200102: {b: 1, c: 2, d: 3},
	* 20200103: {c: 1, d: 2, e: 3},
	* })
	* => {
	* 20200101: {a: 1, b: 2, c: 3, d: 0, e: 0},
	* 20200102: {a: 1, b: 3, c: 5, d: 3, e: 0},
	* 20200103: {a: 1, b: 3, c: 6, d: 5, e: 3},
	import { useState } from 'react'

	export const useStep = <
	T extends {
	[step: string]: string
	}
	>({
	steps,
	initialStep,
	}: {