Intl.DateTimeFormat【国際化日時フォーマット】コンストラクタ・プロパティ・メソッド
new Intl.DateTimeFormat【コンストラクタ】
format【フォーマット関数】
formatRange【範囲フォーマット】
formatRangeToParts【範囲フォーマットパーツ取得】
formatToParts【フォーマットパーツ取得】
resolvedOptions【オプション取得】
supportedLocalesOf【サポート ロケール取得】

var date = new Date(Date.UTC(2001, (2 - 1), 3, 4, 5, 6));
var dtf = new Intl.DateTimeFormat();
console.log(dtf.format(date));
// 出力：2001/2/3

dtf = new Intl.DateTimeFormat("en-US");
console.log(dtf.format(date));
// 出力：2/3/2001

dtf = new Intl.DateTimeFormat("en-GB");
console.log(dtf.format(date));
// 出力：03/02/2001

var options = { year:'2-digit', month:'2-digit', day:'2-digit', hour12:true, hour:'2-digit', minute:'2-digit', second:'2-digit', weekday:'narrow', timeZone:'UTC', timeZoneName:'long' };
dtf = new Intl.DateTimeFormat("en-US", options);
console.log(dtf.format(date));
// 出力：S, 02/03/01, 4:05:06 AM GMT

options = { year:'numeric', month:'numeric', day:'numeric', hour12:false, hour:'2-digit', minute:'numeric', second:'numeric', weekday:'short', timeZone:'Asia/Tokyo', timeZoneName:'short' };
dtf = new Intl.DateTimeFormat("en-US", options);
console.log(dtf.format(date));
// 出力：Sat, 2/3/2001, 13:05:06 GMT+9

options = { year:'2-digit', month:'narrow', day:'2-digit', hour12:true, hour:'2-digit', minute:'2-digit', second:'2-digit', weekday:'long', timeZone:'Asia/Tokyo', timeZoneName:'long' };
dtf = new Intl.DateTimeFormat("en-US", options);
console.log(dtf.format(date));
// 出力：Saturday, F 03, 01, 1:05:06 PM Japan Standard Time

options = { year:'numeric', month:'short', day:'numeric', hour12:false, hour:'numeric', minute:'numeric', second:'numeric', weekday:'narrow', timeZone:'America/New_York', timeZoneName:'short' };
dtf = new Intl.DateTimeFormat("en-US", options);
console.log(dtf.format(date));
// 出力：F, Feb 2, 2001, 23:05:06 EST

options = { year:'2-digit', month:'long', day:'2-digit', hour12:true, hour:'numeric', minute:'2-digit', second:'2-digit', weekday:'short', timeZone:'America/New_York', timeZoneName:'long' };
dtf = new Intl.DateTimeFormat("en-US", options);
console.log(dtf.format(date));
// 出力：Fri, February 02, 01, 11:05:06 PM Eastern Standard Time

options = { era:'narrow', year:'numeric', month:'numeric', day:'numeric', hour:'numeric', minute:'numeric', second:'numeric', weekday:'narrow', hour12:true, timeZoneName:'long' };
dtf = new Intl.DateTimeFormat("ja-JP-u-ca-japanese", options);
console.log(dtf.format(date));
// 出力：H13年2月3日土 13時05分06秒 日本標準時

options = { era:'short', year:'2-digit', month:'2-digit', day:'2-digit',  hour:'2-digit', minute:'2-digit', second:'2-digit', weekday:'short', hour12:false, timeZoneName:'short' };
dtf = new Intl.DateTimeFormat("ja-JP-u-ca-japanese", options);
console.log(dtf.format(date));
// 出力：平成13年02月03日土 13:05:06 JST

options = { era:'long', year:'numeric', month:'numeric', day:'numeric', hour:'numeric', minute:'numeric', second:'numeric', weekday:'long', hour12:true, timeZoneName:'long' };
dtf = new Intl.DateTimeFormat("ja-JP-u-ca-japanese", options);
console.log(dtf.format(date));
// 出力：平成13年2月3日土曜日 13時05分06秒 日本標準時

options = { era:'long', year:'numeric', month:'long', day:'numeric', weekday:'long' };
dtf = new Intl.DateTimeFormat("ja-JP-u-ca-japanese-nu-hanidec", options);
console.log(dtf.format(date));
// 出力：平成一三年二月三日土曜日

dtf = new Intl.DateTimeFormat();
console.log(dtf.format());
// 出力：20xx/x/x 現在日付

new Intl.DateTimeFormat【コンストラクタ】の例を参照

// Array.map【配列変換生成】利用
var days = [ new Date(2001, (2 - 1), 3), new Date(2011, (3 - 1), 4), new Date(2021, (4 - 1), 5) ];
var dtf = new Intl.DateTimeFormat();
console.log(days.map(dtf.format));
// 出力：["2001/2/3", "2011/3/4", "2021/4/5"]

let dateStart = new Date(Date.UTC(2001, (2 - 1), 3, 4, 5, 6));
let dateEnd = new Date(Date.UTC(2002, (3 - 1), 4, 5, 6, 7));

let dtfEfull = new Intl.DateTimeFormat('en-US', { dateStyle: 'full', timeStyle: 'full' })
let dtfElong = new Intl.DateTimeFormat('en-US', { dateStyle: 'long', timeStyle: 'long' })
let dtfEmedium = new Intl.DateTimeFormat('en-US', { dateStyle: 'medium', timeStyle: 'medium' })
let dtfEshort = new Intl.DateTimeFormat('en-US', { dateStyle: 'short', timeStyle: 'short' })
console.log(dtfEfull.formatRange(dateStart, dateEnd));
// 出力例：Saturday, February 3, 2001, 1:05:06 PM Japan Standard Time – Monday, March 4, 2002, 2:06:07 PM Japan Standard Time
console.log(dtfElong.formatRange(dateStart, dateEnd));
// 出力例：February 3, 2001, 1:05:06 PM GMT+9 – March 4, 2002, 2:06:07 PM GMT+9
console.log(dtfEmedium.formatRange(dateStart, dateEnd));
// 出力例：Feb 3, 2001, 1:05:06 PM – Mar 4, 2002, 2:06:07 PM
console.log(dtfEshort.formatRange(dateStart, dateEnd));
// 出力例：2/3/01, 1:05 PM – 3/4/02, 2:06 PM

let dtfJfull = new Intl.DateTimeFormat('ja', { dateStyle: 'full', timeStyle: 'full' })
let dtfJlong = new Intl.DateTimeFormat('ja', { dateStyle: 'long', timeStyle: 'long' })
let dtfJmedium = new Intl.DateTimeFormat('ja', { dateStyle: 'medium', timeStyle: 'medium' })
let dtfJshort = new Intl.DateTimeFormat('ja', { dateStyle: 'short', timeStyle: 'short' })
console.log(dtfJfull.formatRange(dateStart, dateEnd));
// 出力例：2001/2/3土曜日 13時05分06秒 日本標準時～2002/3/4月曜日 14時06分07秒 日本標準時
console.log(dtfJlong.formatRange(dateStart, dateEnd));
// 出力例：2001/2/3 13:05:06 JST～2002/3/4 14:06:07 JST
console.log(dtfJmedium.formatRange(dateStart, dateEnd));
// 出力例：2001/02/03 13:05:06～2002/03/04 14:06:07
console.log(dtfJshort.formatRange(dateStart, dateEnd));
// 出力例：2001/02/03 13:05～2002/03/04 14:06

let date = new Date(Date.UTC(2001, (2 - 1), 3, 4, 5, 6));

let dtfEnglish = new Intl.DateTimeFormat('en-US', { dateStyle: 'full', timeStyle: 'full' })
console.log(dtfEnglish.format(date));
// 出力：Saturday, February 3, 2001 at 1:05:06 PM Japan Standard Time
console.log(dtfEnglish.formatToParts(date));
// 出力：
// Array(17)
// 0: {type: "weekday", value: "Saturday"}
// 1: {type: "literal", value: ", "}
// 2: {type: "month", value: "February"}
// 3: {type: "literal", value: " "}
// 4: {type: "day", value: "3"}
// 5: {type: "literal", value: ", "}
// 6: {type: "year", value: "2001"}
// 7: {type: "literal", value: " at "}
// 8: {type: "hour", value: "1"}
// 9: {type: "literal", value: ":"}
// 10: {type: "minute", value: "05"}
// 11: {type: "literal", value: ":"}
// 12: {type: "second", value: "06"}
// 13: {type: "literal", value: " "}
// 14: {type: "dayPeriod", value: "PM"}
// 15: {type: "literal", value: " "}
// 16: {type: "timeZoneName", value: "Japan Standard Time"}

let dtfJapanese = new Intl.DateTimeFormat('ja-JP', { dateStyle: 'full', timeStyle: 'full' })
console.log(dtfJapanese.format(date));
// 出力：2001年2月3日土曜日 13時05分06秒 日本標準時
console.log(dtfJapanese.formatToParts(date));
// 出力：
// Array(15)
// 0: {type: "year", value: "2001"}
// 1: {type: "literal", value: "年"}
// 2: {type: "month", value: "2"}
// 3: {type: "literal", value: "月"}
// 4: {type: "day", value: "3"}
// 5: {type: "literal", value: "日"}
// 6: {type: "weekday", value: "土曜日"}
// 7: {type: "literal", value: " "}
// 8: {type: "hour", value: "13"}
// 9: {type: "literal", value: "時"}
// 10: {type: "minute", value: "05"}
// 11: {type: "literal", value: "分"}
// 12: {type: "second", value: "06"}
// 13: {type: "literal", value: "秒 "}
// 14: {type: "timeZoneName", value: "日本標準時"}

let dateStart = new Date(Date.UTC(2001, (2 - 1), 3, 4, 5, 6));
let dateEnd = new Date(Date.UTC(2002, (3 - 1), 4, 5, 6, 7));

let dtfEnglish = new Intl.DateTimeFormat('en-US', { dateStyle: 'full', timeStyle: 'full' })
console.log(dtfEnglish.formatRange(dateStart, dateEnd));
// 出力：Saturday, February 3, 2001, 1:05:06 PM Japan Standard Time – Monday, March 4, 2002, 2:06:07 PM Japan Standard Time
console.log(dtfEnglish.formatRangeToParts(dateStart, dateEnd));
// 出力：
// Array(35)
// 0: {type: "weekday", value: "Saturday", source: "startRange"}
// 1: {type: "literal", value: ", ", source: "startRange"}
// 2: {type: "month", value: "February", source: "startRange"}
// 3: {type: "literal", value: " ", source: "startRange"}
// 4: {type: "day", value: "3", source: "startRange"}
// 5: {type: "literal", value: ", ", source: "startRange"}
// 6: {type: "year", value: "2001", source: "startRange"}
// 7: {type: "literal", value: ", ", source: "startRange"}
// 8: {type: "hour", value: "1", source: "startRange"}
// 9: {type: "literal", value: ":", source: "startRange"}
// 10: {type: "minute", value: "05", source: "startRange"}
// 11: {type: "literal", value: ":", source: "startRange"}
// 12: {type: "second", value: "06", source: "startRange"}
// 13: {type: "literal", value: " ", source: "startRange"}
// 14: {type: "dayPeriod", value: "PM", source: "startRange"}
// 15: {type: "literal", value: " ", source: "startRange"}
// 16: {type: "timeZoneName", value: "Japan Standard Time", source: "startRange"}
// 17: {type: "literal", value: " – ", source: "shared"}
// 18: {type: "weekday", value: "Monday", source: "endRange"}
// 19: {type: "literal", value: ", ", source: "endRange"}
// 20: {type: "month", value: "March", source: "endRange"}
// 21: {type: "literal", value: " ", source: "endRange"}
// 22: {type: "day", value: "4", source: "endRange"}
// 23: {type: "literal", value: ", ", source: "endRange"}
// 24: {type: "year", value: "2002", source: "endRange"}
// 25: {type: "literal", value: ", ", source: "endRange"}
// 26: {type: "hour", value: "2", source: "endRange"}
// 27: {type: "literal", value: ":", source: "endRange"}
// 28: {type: "minute", value: "06", source: "endRange"}
// 29: {type: "literal", value: ":", source: "endRange"}
// 30: {type: "second", value: "07", source: "endRange"}
// 31: {type: "literal", value: " ", source: "endRange"}
// 32: {type: "dayPeriod", value: "PM", source: "endRange"}
// 33: {type: "literal", value: " ", source: "endRange"}
// 34: {type: "timeZoneName", value: "Japan Standard Time", source: "endRange"}

let dtfJapanese = new Intl.DateTimeFormat('ja-JP', { dateStyle: 'full', timeStyle: 'full' })
console.log(dtfJapanese.formatRange(dateStart, dateEnd));
// 出力：2001/2/3土曜日 13時05分06秒 日本標準時～2002/3/4月曜日 14時06分07秒 日本標準時
console.log(dtfJapanese.formatRangeToParts(dateStart, dateEnd));
// 出力：
// Array(29)
// 0: {type: "year", value: "2001", source: "startRange"}
// 1: {type: "literal", value: "/", source: "startRange"}
// 2: {type: "month", value: "2", source: "startRange"}
// 3: {type: "literal", value: "/", source: "startRange"}
// 4: {type: "day", value: "3", source: "startRange"}
// 5: {type: "weekday", value: "土曜日", source: "startRange"}
// 6: {type: "literal", value: " ", source: "startRange"}
// 7: {type: "hour", value: "13", source: "startRange"}
// 8: {type: "literal", value: "時", source: "startRange"}
// 9: {type: "minute", value: "05", source: "startRange"}
// 10: {type: "literal", value: "分", source: "startRange"}
// 11: {type: "second", value: "06", source: "startRange"}
// 12: {type: "literal", value: "秒 ", source: "startRange"}
// 13: {type: "timeZoneName", value: "日本標準時", source: "startRange"}
// 14: {type: "literal", value: "～", source: "shared"}
// 15: {type: "year", value: "2002", source: "endRange"}
// 16: {type: "literal", value: "/", source: "endRange"}
// 17: {type: "month", value: "3", source: "endRange"}
// 18: {type: "literal", value: "/", source: "endRange"}
// 19: {type: "day", value: "4", source: "endRange"}
// 20: {type: "weekday", value: "月曜日", source: "endRange"}
// 21: {type: "literal", value: " ", source: "endRange"}
// 22: {type: "hour", value: "14", source: "endRange"}
// 23: {type: "literal", value: "時", source: "endRange"}
// 24: {type: "minute", value: "06", source: "endRange"}
// 25: {type: "literal", value: "分", source: "endRange"}
// 26: {type: "second", value: "07", source: "endRange"}
// 27: {type: "literal", value: "秒 ", source: "endRange"}
// 28: {type: "timeZoneName", value: "日本標準時", source: "endRange"}

var dtf = new Intl.DateTimeFormat();
console.log(dtf.resolvedOptions());
// 出力：
// object {
// calendar:"gregory"
// day:"numeric"
// locale:"ja"
// month:"numeric"
// numberingSystem:"latn"
// timeZone:"Asia/Tokyo"
// year:"numeric"
// }

console.log(dtf.format());
// 出力：20xx/xx/xx 現在日付

console.log(Intl.DateTimeFormat.supportedLocalesOf('ja'));
// 出力例：Array [ "ja" ]

console.log(Intl.DateTimeFormat.supportedLocalesOf('ng'));
// 出力例：Array []

let locales = ['ng', 'ja', 'ja-JP', 'en', 'en-US', 'en-GB'];
console.log(Intl.DateTimeFormat.supportedLocalesOf(locales));
// 出力例：Array(5) [ "ja", "ja-JP", "en", "en-US", "en-GB" ]

locales = ['ng', 'jpn', 'jpn-JP', 'eng', 'eng-US', 'eng-GB'];
console.log(Intl.DateTimeFormat.supportedLocalesOf(locales));
// 出力例：Array(5) [ "ja", "ja-JP", "en", "en-US", "en-GB" ]

console.log(Intl.DateTimeFormat.supportedLocalesOf(locales, { localeMatcher: 'lookup' }));
// 出力例：Array(5) [ "ja", "ja-JP", "en", "en-US", "en-GB" ]