node-recurring/lib/index.js

A super simple JavaScript library for defining recurring schedules and calculating occurrences for them

'use strict'
const moment = require('moment')
const _ = require('underscore')._

if (!Number.prototype.pad) {
  Number.prototype.pad = function (size) {
    var s = String(this)
    while (s.length < (size || 2)) {
      s = '0' + s
    }
    return s
  }
}

exports = module.exports = function (config) {
  config.options = config.options || {}
  config.options.format = config.options.format || 'YYYY-MM-DD'
  config.iterations = config.iterations || 50
  config.limit = config.limit || null
  config.start = moment(config.start)
  config.end = config.end ? moment(config.end) : null

  const occurrence = config.start

  if (config.dayOfMonth) {
    while (true) {
      if (occurrence.date() === config.dayOfMonth) {
        break
      }

      occurrence.add(1, 'd')
    }
  }

  if (config.weekday || config.weekday === 0) {
    while (true) {
      if (occurrence.weekday() === config.weekday) {
        break
      }
      occurrence.add(1, 'd')
    }
  }

  const results = []
  let iterations = 0
  let lastBaseOccurrence = null

  if (config.interval === 'd' && config.options.skipWeekend) {
    let weekdayIndex = 0;

    while (
      (!config.limit || results.length < config.limit) &&
      (!config.iterations || iterations < config.iterations) &&
      (!config.end || occurrence.isSameOrBefore(config.end))
    ) {
      const day = occurrence.weekday()
      if (day !== 0 && day !== 6) {
        if (weekdayIndex % config.every === 0) {
          results.push(occurrence.format(config.options.format));
          iterations++;
          lastBaseOccurrence = occurrence.format(config.options.format)
        }
        weekdayIndex++;
      }

      occurrence.add(1, 'd');
    }

    return {
      results: results,
      iterations: iterations,
      info: {
        lastBaseOccurrence: lastBaseOccurrence
      }
    }
  }

  while (true) {
    iterations++

    let result = occurrence
    if (config.dayOfMonth) {
      const expectedDate = moment(result).format('YYYY-MM-') + config.dayOfMonth.pad(2)
      result = moment(expectedDate)
    }
    if (config.options.skipWeekend && result.isValid()) {
      if (result.weekday() === 0) {
        result = result.clone().add(1, 'd')
      }

      if (result.weekday() === 6) {
        result = result.clone().add(2, 'd')
      }
    }

    const formattedResult = result.format(config.options.format)
    if (!_.contains(results, formattedResult) && result.isValid()) {
      results.push(formattedResult)
    }

    lastBaseOccurrence = occurrence.format(config.options.format)
    occurrence.add(config.every, config.interval)

    if (config.end !== null && occurrence.isAfter(config.end)) {
      break
    }

    if (config.limit !== null && results.length >= config.limit) {
      break
    }

    if (iterations >= config.iterations) {
      break
    }
  }

  return {
    results: results,
    iterations: iterations,
    info: {
      lastBaseOccurrence: lastBaseOccurrence
    }
  }
}