index.js
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var parse = require('../parse/index.js')
var MILLISECONDS_IN_DAY = 24 * 60 * 60 * 1000
/**
* @category Range Helpers
* @summary Get the number of days that overlap in two date ranges
*
* @description
* Get the number of days that overlap in two date ranges
*
* @param {Date|String|Number} initialRangeStartDate - the start of the initial range
* @param {Date|String|Number} initialRangeEndDate - the end of the initial range
* @param {Date|String|Number} comparedRangeStartDate - the start of the range to compare it with
* @param {Date|String|Number} comparedRangeEndDate - the end of the range to compare it with
* @returns {Number} the number of days that overlap in two date ranges
* @throws {Error} startDate of a date range cannot be after its endDate
*
* @example
* // For overlapping date ranges adds 1 for each started overlapping day:
* getOverlappingDaysInRanges(
* new Date(2014, 0, 10), new Date(2014, 0, 20), new Date(2014, 0, 17), new Date(2014, 0, 21)
* )
* //=> 3
*
* @example
* // For non-overlapping date ranges returns 0:
* getOverlappingDaysInRanges(
* new Date(2014, 0, 10), new Date(2014, 0, 20), new Date(2014, 0, 21), new Date(2014, 0, 22)
* )
* //=> 0
*/
function getOverlappingDaysInRanges (dirtyInitialRangeStartDate, dirtyInitialRangeEndDate, dirtyComparedRangeStartDate, dirtyComparedRangeEndDate) {
var initialStartTime = parse(dirtyInitialRangeStartDate).getTime()
var initialEndTime = parse(dirtyInitialRangeEndDate).getTime()
var comparedStartTime = parse(dirtyComparedRangeStartDate).getTime()
var comparedEndTime = parse(dirtyComparedRangeEndDate).getTime()
if (initialStartTime > initialEndTime || comparedStartTime > comparedEndTime) {
throw new Error('The start of the range cannot be after the end of the range')
}
var isOverlapping = initialStartTime < comparedEndTime && comparedStartTime < initialEndTime
if (!isOverlapping) {
return 0
}
var overlapStartDate = comparedStartTime < initialStartTime
? initialStartTime
: comparedStartTime
var overlapEndDate = comparedEndTime > initialEndTime
? initialEndTime
: comparedEndTime
var differenceInMs = overlapEndDate - overlapStartDate
return Math.ceil(differenceInMs / MILLISECONDS_IN_DAY)
}
module.exports = getOverlappingDaysInRanges