JavaScript之通过年月获取月份的天数、日期格式化、时间、补零、Date、toLocaleString、Intl、DateTimeFormat、format(问题总结)

function createDays(year = 2024, month = 2) {
    let sDate = new Date(year, month - 1, 1),
        eDate = new Date(year, month, 0),
        days = [];
    sDate = sDate.getDate();
    eDate = eDate.getDate();
    for (let i = sDate; i <= eDate; i++) {
        let ds = new Date(year, month - 1, i);
        ds = ds.toLocaleString("en-US", { timeZone: "Asia/Shanghai" });
        ds = ds.split(',')[0];
        ds = ds.split('/');
        [ds[0], ds[1], ds[2]] = [ds[2], ('0' + ds[0]).slice(-2), ('0' + ds[1]).slice(-2)];
        ds = ds.toString();
        ds = ds.replace(/,/g, '-');
        days.push(ds);
    }
    return days;
}
console.log(createDays(2023, 1));
console.log(createDays(2023, 2));
console.log(createDays());

function createDays(year = 2024, month = 2) {
    let sDate = new Date(year, month - 1, 1),
        eDate = new Date(year, month, 0),
        formatter = new Intl.DateTimeFormat('default', {
            timeZone: 'Asia/Shanghai',
            year: 'numeric',
            month: 'numeric',
            day: 'numeric'
        }),
        zeroFill = (val) => ('00' + val).slice(-2),
        days = [];
    sDate = sDate.getDate();
    eDate = eDate.getDate();
    for (let i = sDate; i <= eDate; i++) {
        let ds = new Date(year, month - 1, i);
        ds = formatter.format(ds);
        ds = ds.split('/');
        ds[1] = zeroFill(ds[1]);
        ds[2] = zeroFill(ds[2]);
        ds = ds.toString();
        ds = ds.replace(/,/g, '-');
        days.push(ds);
    }
    return days;
}
console.log(createDays(2023, 1));
console.log(createDays(2023, 2));
console.log(createDays());

function createDays(year = 2024, month = 2) {
    let sDate = new Date(year, month - 1, 1),
        eDate = new Date(year, month, 0),
        zeroFill = (val) => ('00' + val).slice(-2),
        days = [];
    sDate = sDate.getDate();
    eDate = eDate.getDate();
    for (let i = sDate; i <= eDate; i++) {
        let ds = new Date(year, month - 1, i);
        ds = ds.toLocaleString(
            "en-US",
            {
                timeZone: "Asia/Shanghai",
                year: 'numeric',
                month: 'numeric',
                day: 'numeric'
            }
        );
        ds = ds.split('/');
        [ds[0], ds[1], ds[2]] = [ds[2], zeroFill(ds[0]), zeroFill(ds[1])];
        ds = ds.toString();
        ds = ds.replace(/,/g, '-');
        days.push(ds);
    }
    return days;
}
console.log(createDays(2023, 1));
console.log(createDays(2023, 2));
console.log(createDays());

// 创建一个表示当前日期和时间的对象
var currentDate = new Date();
// 使用毫秒数创建一个日期对象
var dateFromMilliseconds = new Date(1629194400000);
// 使用字符串创建一个日期对象
var dateFromString = new Date("2024-03-05T12:00:00");
// 使用年、月、日创建一个日期对象
var dateFromYMD = new Date(2024, 2, 5); // 月份从0开始，所以3月是2
// 使用 ISO 格式字符串创建一个日期对象
var dateFromISOString = new Date("2024-03-05T12:00:00Z");

var number = 123456.789;
console.log(number.toLocaleString('en-US'));
// 输出: 123,456.789 (使用美国英语格式)
console.log(number.toLocaleString('de-DE'));
// 输出: 123.456,789 (使用德国德语格式)

var number = 123456.789;
var options = {
  style: 'currency',
  currency: 'EUR',
  minimumFractionDigits: 2,
  maximumFractionDigits: 2
};
console.log(number.toLocaleString('de-DE', options)); 
// 输出: €123,456.79 (使用德国德语格式，货币为欧元，小数位数为两位)

var date = new Date();
var options = { dateStyle: 'full', timeStyle: 'short' };
console.log(date.toLocaleString('en-US', options));
// 输出: Saturday, March 5, 2024 at 1:30 PM (使用美国英语格式)

const now = new Date();
// 通过 Intl.DateTimeFormat 构造函数创建一个日期格式化对象，设置 timeZone 为 'Asia/Shanghai'（中国时区）
const formatter = new Intl.DateTimeFormat('default', {
  timeZone: 'Asia/Shanghai',
  year: 'numeric',
  month: 'numeric',
  day: 'numeric',
  hour: 'numeric',
  minute: 'numeric',
  second: 'numeric',
});
// 使用格式化对象将日期对象转换为字符串
const formattedDate = formatter.format(now);
console.log(formattedDate);