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js 获取是否为闰年，以及各月的天数

calendar utils

isLeapYear

const isLeapYear = (year) => {
    return (year % 4 === 0) && (year % 100 !== 0 || year % 400 === 0);
}

const year = new Date().getFullYear()

isLeapYear(year);

getMonthDays

const getMonthDays = (timestamp) => {
  const date = new Date(timestamp);
  const year = date.getFullYear();
  const month = date.getMonth() + 1;
  let days = 0;
  switch (month) {
    case 1:
    case 3:
    case 5:
    case 7:
    case 8:
    case 10:
    case 12:
      days = 31;
      break;
    case 2:
      if(isLeapYear(year)) {
        days = 29;
      } else {
        days = 28;
      }
      break;
    case 4:
    case 6:
    case 9:
    case 11:
      days = 30;
      break;
    default:
      break;
  }
  return days;
}

function isLeapYear(year) {
  // 如果year年2月没有29则自动进一变为3月1日
  var date = new Date(year, 1, 29)
  return date.getDate() === 29
}

isLeapYear(2000) // true
isLeapYear(2001) // false


// 将时间设置为这个月的下一月的第一天，然后回拨一秒


function monthDay(year, month) {
  var date = new Date(year, month, 1, 0, 0, 0)
  var yesterDay = new Date(date - 1000)
  return yesterDay.getDate()
}
monthDay(2017, 2)  // 28
monthDay(2017, 12)  // 31

isToday

const isToday = (timestamp = ``) => {
  return new Date(timestamp).toLocaleDateString() === new Date().toLocaleDateString();
}

format today

const autoGetToday = (time = ``, debug = false) => {
    let log = console.log;
    let date = new Date();
    let year = date.getFullYear();
    let month = date.getMonth() + 1;
    let day = date.getDate();
    if (debug) {
        log(year);
        log(month);
        log(day);
    }
    let today = `${year}/${month}/${day} ${time}`;
    if (debug) {
        log(`today =`, today);
    }
    return today;
};

refs

https://www.cnblogs.com/xgqfrms/p/12661145.html

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