js-localdate-plus/js-localdate-plus.js

JS library inspired by localdate.Fix bugs and add new temporal feature.

/**
 *  LocalDate - immutable object representing an ISO-8601 date
 *  Homepage  : https://github.com/LinusLing/js-localdate-plus
 *  Author    : Linus Ling
 *  License   : MIT
 */

(function () {

  'use strict';

  var _days = [0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];

  function toJulianDay(year, month, day) {
    if (month <= 2) {
      year -= 1;
      month += 12;
    }

    var A = Math.floor(year / 100);
    var B = 2 - A + Math.floor(A / 4);

    return Math.floor(365.25 * (year + 4716)) + Math.floor(30.6001 * (month + 1)) + day + B - 1524;
  }

  function fromJulianDay(d) {
    var a = Math.floor((d - 1867216.25) / 36524.25);
    var A = d < 2299161 ? d : d + 1 + a - Math.floor(a / 4);

    var B = A + 1524;
    var C = Math.floor((B - 122.1) / 365.25);
    var D = Math.floor(365.25 * C);
    var E = Math.floor((B - D) / 30.6001);

    var day = B - D - Math.floor(30.6001 * E);
    var month = E < 14 ? E - 1 : E - 13;
    var year = month > 2 ? C - 4716 : C - 4715;

    return new LocalDate(year, month, Math.floor(day));
  }

  function fromString(date) {
    return new (LocalDate.bind.apply(LocalDate, [null].concat(date.split('-'))));
  }

  function fromDate(date) {
    return new LocalDate(date.getFullYear(), date.getMonth() + 1, date.getDate());
  }

  /**
   * @constructor
   */
  function LocalDate(a, b, c) {
    if (arguments.length === 0) {
      return fromDate(new Date);
    } else if (arguments.length === 1) {
      if (typeof a === 'undefined' || a === null || a === '') {
        return fromDate(new Date);
      } else if (typeof a === 'string') {
        return fromString(a);
      } else if (a instanceof Date) {
        return fromDate(a);
      } else {
        return fromJulianDay(a);
      }
    }

    this.year = parseInt(a, 10);
    this.month = parseInt(b, 10);
    this.day = parseInt(c, 10);

    this.value = toJulianDay(this.year, this.month, this.day);
  }

  LocalDate.prototype.clone = function () {
    return new LocalDate(this.year, this.month, this.day);
  }

  LocalDate.prototype.equals = function (date) {
    return this.diff(date) === 0;
  }

  LocalDate.prototype.isBefore = function (date) {
    return this.diff(date) < 0;
  }

  LocalDate.prototype.isAfter = function (date) {
    return this.diff(date) > 0;
  }

  LocalDate.prototype.diff = function (date) {
    return this.value - (date instanceof LocalDate ? date.valueOf() : new LocalDate(date).valueOf());
  }

  LocalDate.prototype.toString = function () {
    var month = this.month < 10 ? '0' + this.month : this.month;
    var day = this.day < 10 ? '0' + this.day : this.day;

    return this.year + '-' + month + '-' + day;
  }

  LocalDate.prototype.toDate = function () {
    return new Date(this.year, this.month - 1, this.day);
  }

  LocalDate.prototype.toJulianDay = function () {
    return this.value;
  }

  LocalDate.prototype.toJSON = function () {
    return this.toString();
  }

  LocalDate.prototype.valueOf = function () {
    return this.value;
  }

  LocalDate.prototype.isValid = function () {
    if (this.year === 0) {
      return false;
    }

    if (this.month < 1 || this.month > 12) {
      return false;
    }

    if (this.day < 1 || this.day > this.lengthOfMonth()) {
      return false;
    }

    return !isNaN(this.year) && !isNaN(this.month) && !isNaN(this.day);
  }

  LocalDate.prototype.isLeapYear = function (year) {
    var test = year || this.year;

    return ((test % 4) === 0) && ((test % 100) !== 0 || (test % 400) === 0);
  }

  LocalDate.prototype.lengthOfMonth = function (month, year) {
    var test = month || this.month;

    return _days[test] + (test === 2 && this.isLeapYear(year));
  }

  LocalDate.prototype.lengthOfYear = function (year) {
    return 365 + this.isLeapYear(year);
  }

  LocalDate.prototype.getDayOfYear = function () {
    return this.day + (this.month > 2 && this.isLeapYear()) + _days.slice(1, this.month).reduce(function (n, a) { return n + a }, 0);
  }

  LocalDate.prototype.getDayOfWeek = function () {
    return this.toDate().getDay();
  }

  LocalDate.prototype.getDay = function () {
    return this.day;
  }

  LocalDate.prototype.getMonth = function () {
    return this.month;
  }

  LocalDate.prototype.getYear = function () {
    return this.year;
  }

  LocalDate.prototype.setDay = function (day) {
    return new LocalDate(this.year, this.month, day);
  }

  LocalDate.prototype.setMonth = function (month) {
    return new LocalDate(this.year, month, this.day);
  }

  LocalDate.prototype.setYear = function (year) {
    return new LocalDate(year, this.month, this.day);
  }

  LocalDate.prototype.addYears = function (years) {
    var year = this.year + years;
    var day = Math.min(this.day, this.lengthOfMonth(this.month, year));

    return new LocalDate(year, this.month, day);
  }

  LocalDate.prototype.addMonths = function (months) {
    var year = this.year;
    var month = this.month + Math.abs(months);

    while (month > 12) {
      month -= 12;
      year += 1;
    }

    var day = Math.min(this.day, this.lengthOfMonth(month, year));

    return new LocalDate(year, month, day);
  }

  LocalDate.prototype.addDays = function (days) {
    var year = this.year;
    var month = this.month;
    var day = this.day + Math.abs(days);

    while (day > this.lengthOfMonth(month, year)) {
      day -= this.lengthOfMonth(month, year);
      month += 1;

      if (month > 12) {
        month = 1;
        year += 1;
      }
    }

    return new LocalDate(year, month, day);
  }

  LocalDate.prototype.subtractYears = function (years) {
    var year = this.year - years;
    var day = Math.min(this.day, this.lengthOfMonth(this.month, year));
    return new LocalDate(year, this.month, day);
  }

  LocalDate.prototype.subtractMonths = function (months) {
    var year = this.year;
    var month = this.month - Math.abs(months);

    while (month < 1) {
      month += 12;
      year -= 1;
    }

    var day = Math.min(this.day, this.lengthOfMonth(month, year));

    return new LocalDate(year, month, day);
  }

  LocalDate.prototype.subtractDays = function (days) {
    var year = this.year;
    var month = this.month;
    var day = this.day - Math.abs(days);

    while (day < 1) {
      if (month - 1 < 1) {
        month = 13;
        year -= 1;
      }

      day += this.lengthOfMonth(month - 1, year);
      month -= 1;
    }

    return new LocalDate(year, month, day);
  }

  // WithGap means: When adding years/months, if the original day of the month is greater than the number of days in the final month, the final month will change to the next month and the final day will be the first day plus gap days in the final month. It's similar to the conception of Carry in arithmetic.
  LocalDate.prototype.addYearsWithGap = function (years) {
    var year = this.year + years;
    var day = Math.min(this.day, this.lengthOfMonth(this.month, year));
    var gap_day = Math.abs(this.day - this.lengthOfMonth(this.month, year));
    return (new LocalDate(year, this.month, day)).addDays(gap_day);
  }

  LocalDate.prototype.addMonthsWithGap = function (months) {
    var year = this.year;
    var month = this.month + Math.abs(months);

    while (month > 12) {
      month -= 12;
      year += 1;
    }

    var day = Math.min(this.day, this.lengthOfMonth(month, year));
    var gap_day = Math.abs(this.day - this.lengthOfMonth(month, year));
    return (new LocalDate(year, month, day)).addDays(gap_day);
  }

  if (typeof module !== 'undefined' && typeof module.exports !== 'undefined') {
    module.exports = LocalDate;
  } else {
    window.LocalDate = LocalDate;
  }
})();