date-util.js

//                     year       month    date
var RE_DATE = /^([+-]?\d{4,6})\-(\d\d)\-(\d\d)$/
var RE_MONTH = /^([+-]?\d{4,6})\-(\d\d)$/
var RE_TIME = /^(\d\d):(\d\d)(?::(\d\d))?$/
var RE_WEEK = /^([+-]?\d{4,6})-W(\d\d)(?:-?(\d))?$/
var RE_DATETIME = /^([+-]?\d{4,6})\-(\d\d)\-(\d\d)T(\d\d):(\d\d)(?::(\d\d))?(?:[+-]\d\d:\d\d)?Z?$/;

function toInt(string) {
  return parseInt(string, 10)
}

function fixWeekday(weekday){
  return weekday === 0 ? 7 : weekday
}

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

var MONTH_DATES = [31, 28, 31, 30, 31, 30, 30, 31, 30, 31, 30, 31]
// 计算指定年份所在月的天数
function getDaysOfMonth(year, month){
  return MONTH_DATES[month] + (month === 1 && isLeapYear(year) ? 1 : 0)
}

// 计算指定年份第 week 周的周一 0 时的时间。
function getDateOfWeek(year, week, weekday) {
  var dow = new Date(year, 0, 1).getDay()
  var dates = 1 + (week - 1) * 7
  if (1 <= dow && dow <= 4) {
    dates -= dow - 1
  } else {
    dates += 8 - dow
  }
  return new Date(year, 0, dates + (weekday || 1) - 1)
}

// 计算指定年份拥有的周数
// 第 1 周的周四，第 53 周的周四
function getWeeksOfYear(year) {
  var firstWeek = getDateOfWeek(year, 1, 4)
  var lastWeek = getDateOfWeek(year, 53, 4)
  return 52 +
    (firstWeek.getFullYear() !== year ? 1 : 0) +
    (lastWeek.getFullYear() === year ? 1 : 0)
}

function parseDate(string) {
  var match
  var year = 1900
  var month = 0
  var date = 1
  var hours = 0
  var minutes = 0
  var seconds = 0
  var milliseconds = 0

  if (match = RE_DATE.exec(string)) {

    year = toInt(match[1])
    month = toInt(match[2]) - 1
    date = toInt(match[3])

  } else if (match = RE_MONTH.exec(string)) {

    year = toInt(match[1])
    month = toInt(match[2]) - 1

  } else if (match = RE_TIME.exec(string)) {

    hours = toInt(match[1])
    minutes = toInt(match[2])
    seconds = toInt(match[3]) || 0

  } else if (match = RE_WEEK.exec(string)) {

    var y = toInt(match[1])
    var w = toInt(match[2])
    // Unset `match[3]`, day is NaN. NaN < 0 && NaN <0
    // Do'nt set default day by `|| 1`, it will effect weekdayrange [1,7] limit.
    var day = toInt(match[3])
    var maxWeeks = getWeeksOfYear(y)
    if (1 > w || w > maxWeeks || 1 > day || day > 7) {
      return NaN
    }
    var d = getDateOfWeek(y, w, day)
    year = d.getFullYear()
    month = d.getMonth()
    date = d.getDate()

  } else if (match = RE_DATETIME.exec(string)) {

    year = toInt(match[1])
    month = toInt(match[2]) - 1
    date = toInt(match[3])
    hours = toInt(match[4])
    minutes = toInt(match[5])
    seconds = toInt(match[6]) || 0
    milliseconds = toInt(match[7]) || 0

  } else {

    return NaN

  }

  if (0 > month || month > 11 ||
      1 > date || date > getDaysOfMonth(year, month) ||
      0 > hours || hours > 23 ||
      0 > minutes || minutes > 59 ||
      0 > seconds || seconds > 59 ||
      0 > milliseconds || milliseconds > 999
      ) {

    return NaN
  }

  // Use 1900(or another year) and setFullYear for fix new Date(year, ...) not support [0,99] year.
  var dt = new Date(1900, month, date, hours, minutes, seconds, milliseconds)
  dt.setFullYear(year)

  return dt
}

function distanceDate(stringA, stringB) {
  var dateA = parseDate(stringA)
  var dateB = parseDate(stringB)
  if (isNaN(dateA) || isNaN(dateB)) {throw new Error('Invalid Date'); }
  return dateA.getTime() - dateB.getTime()
}

function compareDate(stringA, stringB) {
  var distance = distanceDate(stringA, stringB)
  if (distance === 0) {return 0}
  return distance > 0 ? 1 : -1
}

function isDate(string) {
  var match = string.match(RE_DATE)
  return RE_DATE.test(string) && !isNaN(parseDate(string))
}

function isDateTime(string){
  return RE_DATETIME.test(string) && !isNaN(parseDate(string))
}

function isMonth(string){
  return RE_MONTH.test(string) && !isNaN(parseDate(string))
}

function isTime(string){
  return RE_TIME.test(string) && !isNaN(parseDate(string))
}

function isWeek(string){
  return RE_WEEK.test(string) && !isNaN(parseDate(string))
}

module.exports = {
  getDateOfWeek: getDateOfWeek,
  parseDate: parseDate,
  getWeeksOfYear: getWeeksOfYear,
  compareDate: compareDate,
  distanceDate: distanceDate,
  isDate: isDate,
  isDateTime: isDateTime,
  isMonth: isMonth,
  isTime: isTime,
  isWeek: isWeek
}