tempex

Temporal Expressions in Javascript

Introduction

Temporal expressions allow defining and querying recurring events on calendars. This little library roughly follows the ideas of Martin Fowler's article about recurring events.

Example: Races take place Wednesdays in summer (September until April, in the Southern Hemisphere) and Saturdays in winter (May until August).

var t = require('tempex');

var winterMonths = t.months([4, 5, 6, 7]); // we use Javascript convention: May=4, June=5, ...
var summerMonths = t.negate(winterMonths);
var raceSchedule = t.union([
  // summer
  t.intersectionOf(
    summerMonths,
    t.onWeekdays([ 3 ]) // Wednesday=3
  ),
  // winter
  t.intersectionOf(
    winterMonths,
    t.onWeekdays([ 6 ]) // Saturdays=6
  ),
])

To determine the actual occurrences (days) of this schedule in a time range:

t.occurrences(raceSchedule, new Date(2015, 2, 1), new Date(2015, 5, 31));

will produce:

[ Wed Mar 04 2015 00:00:00 GMT+0200 (SAST),
  Wed Mar 11 2015 00:00:00 GMT+0200 (SAST),
  Wed Mar 18 2015 00:00:00 GMT+0200 (SAST),
  Wed Mar 25 2015 00:00:00 GMT+0200 (SAST),
  Wed Apr 01 2015 00:00:00 GMT+0200 (SAST),
  Wed Apr 08 2015 00:00:00 GMT+0200 (SAST),
  Wed Apr 15 2015 00:00:00 GMT+0200 (SAST),
  Wed Apr 22 2015 00:00:00 GMT+0200 (SAST),
  Wed Apr 29 2015 00:00:00 GMT+0200 (SAST),
  Sat May 02 2015 00:00:00 GMT+0200 (SAST),
  Sat May 09 2015 00:00:00 GMT+0200 (SAST),
  Sat May 16 2015 00:00:00 GMT+0200 (SAST),
  Sat May 23 2015 00:00:00 GMT+0200 (SAST),
  Sat May 30 2015 00:00:00 GMT+0200 (SAST),
  Sat Jun 06 2015 00:00:00 GMT+0200 (SAST),
  Sat Jun 13 2015 00:00:00 GMT+0200 (SAST),
  Sat Jun 20 2015 00:00:00 GMT+0200 (SAST),
  Sat Jun 27 2015 00:00:00 GMT+0200 (SAST) ]

If we want to express that there won't be races during the Easter holidays:

var holidays = t.intersectionOf( t.onOrAfter(new Date(2015, 2, 30)), t.onOrBefore(new Date(2015, 3, 17))) var raceDays = t.intersectionOf(raceSchedule, t.negate(holidays))

Then

t.occurrences(raceDays, new Date(2015, 2, 1), new Date(2015, 5, 31))

will give us the occurrences:

[ Wed Mar 04 2015 00:00:00 GMT+0200 (SAST),
  Wed Mar 11 2015 00:00:00 GMT+0200 (SAST),
  Wed Mar 18 2015 00:00:00 GMT+0200 (SAST),
  Wed Mar 25 2015 00:00:00 GMT+0200 (SAST),
  Wed Apr 22 2015 00:00:00 GMT+0200 (SAST),
  Wed Apr 29 2015 00:00:00 GMT+0200 (SAST),
  Sat May 02 2015 00:00:00 GMT+0200 (SAST),
  Sat May 09 2015 00:00:00 GMT+0200 (SAST),
  Sat May 16 2015 00:00:00 GMT+0200 (SAST),
  Sat May 23 2015 00:00:00 GMT+0200 (SAST),
  Sat May 30 2015 00:00:00 GMT+0200 (SAST),
  Sat Jun 06 2015 00:00:00 GMT+0200 (SAST),
  Sat Jun 13 2015 00:00:00 GMT+0200 (SAST),
  Sat Jun 20 2015 00:00:00 GMT+0200 (SAST),
  Sat Jun 27 2015 00:00:00 GMT+0200 (SAST) ]

API Documentation

Is here.