Check if more than two date ranges overlap

Here is refined version of what Paul posted:

• Added filter and null check to allow any number of entries
• Changed the logic so that it can be applied on an array. Eg: [{"from": value, "to": value}]
• Adjusted overlap check to allow times having end and start as same

Script:

function dateRangeOverlaps(a_start, a_end, b_start, b_end) {
    if (a_start < b_start && b_start < a_end) return true; // b starts in a
    if (a_start < b_end   && b_end   < a_end) return true; // b ends in a
    if (b_start <  a_start && a_end   <  b_end) return true; // a in b
    return false;
}

function multipleDateRangeOverlaps(timeEntries) {
    let i = 0, j = 0;
    let timeIntervals = timeEntries.filter(entry => entry.from != null && entry.to != null && entry.from.length === 8 && entry.to.length === 8);

    if (timeIntervals != null && timeIntervals.length > 1)
    for (i = 0; i < timeIntervals.length - 1; i += 1) {
        for (j = i + 1; j < timeIntervals.length; j += 1) {
                if (
                dateRangeOverlaps(
            timeIntervals[i].from.getTime(), timeIntervals[i].to.getTime(),
            timeIntervals[j].from.getTime(), timeIntervals[j].to.getTime()
                    )
                ) return true;
            }
        }
   return false;
}

//storing existing dates for comparison

public multipleExistingDates=[
         {startDate:'02/03/2020 05:00:00',endDate:'02/03/2020 05:30:00'},
         {startDate:02/04/2020 05:00:00'',endDate:'02/05/2020 05:00:00'},]

/The date to be compared with existing dates to check if the new date is overlapping with existing dates/

public checkOverlappingDsates(startDate:Date, endDate:Date):boolean{
  return this.multipleExistingDates.some((elem)=>{
       return( !((moment(endDate).diff(moment(elem.startDate))) < 0 || 
              (moment(startDate).diff(moment(elem.endDate))) > 0;})

Note: If the date is overlapping, the function return true else false. Also , you would need to install moment for date comparison.

You can use nested for loops with arguments

function dateRangeOverlaps(a_start, a_end, b_start, b_end) {
    if (a_start <= b_start && b_start <= a_end) return true; // b starts in a
    if (a_start <= b_end   && b_end   <= a_end) return true; // b ends in a
    if (b_start <  a_start && a_end   <  b_end) return true; // a in b
    return false;
}
function multipleDateRangeOverlaps() {
    var i, j;
    if (arguments.length % 2 !== 0)
        throw new TypeError('Arguments length must be a multiple of 2');
    for (i = 0; i < arguments.length - 2; i += 2) {
        for (j = i + 2; j < arguments.length; j += 2) {
            if (
                dateRangeOverlaps(
                    arguments[i], arguments[i+1],
                    arguments[j], arguments[j+1]
                )
            ) return true;
        }
    }
    return false;
}

Below code comes from my project, maybe it will help you:

function dateRangeOverlaps(startDateA, endDateA, startDateB, endDateB) {

    if ((endDateA < startDateB) || (startDateA > endDateB)) {
        return null
    }

    var obj = {};
    obj.startDate = startDateA <= startDateB ? startDateB : startDateA;
    obj.endDate = endDateA <= endDateB ? endDateA : endDateB;

    return obj;
}