Quick and easy dates ranges overlap check

isRangesOverlap.ts

export function isRangesOverlap(
    firstRange: [Date, Date],
    secondRange: [Date, Date]
): boolean {
    const firstRangeStart = firstRange[0].getTime();
    const secondRangeStart = secondRange[0].getTime();

    const firstRangeEnd = firstRange[1].getTime();
    const secondRangeEnd = secondRange[1].getTime();

    const firstComparatorStart = firstRangeStart > secondRangeStart ? secondRangeStart : firstRangeStart;
    const secondComparatorStart = firstRangeStart > secondRangeStart ? firstRangeStart : secondRangeStart;

    const firstComparatorEnd = firstRangeEnd > secondRangeEnd ? secondRangeEnd : firstRangeEnd;
    const secondComparatorEnd = firstRangeEnd > secondRangeEnd ? firstRangeEnd : secondRangeEnd;

    // 10...20
    // 12...24
    // 10 < 12 && 24 > 20

    if (firstComparatorStart < secondComparatorStart && secondComparatorEnd > firstComparatorEnd) {
        return true;
    }

    // 10...15
    // 12...13
    // 10 < 12 && 13 < 15

    if (firstComparatorStart < secondComparatorStart && secondComparatorEnd < firstComparatorEnd) {
        return true;
    }

    // 10...15
    // 09...11
    // 10 > 09 && 11 < 15

    if (firstComparatorStart > secondComparatorStart && secondComparatorEnd < firstComparatorEnd) {
        return true;
    }


    return false;
}

console.log(
    isRangesOverlap(
        [new Date(2024, 3, 12), new Date(2024, 3, 24)],
        [new Date(2024, 3, 10), new Date(2024, 3, 20)],
    )
)

console.log(
    isRangesOverlap(
        [new Date(2024, 3, 12), new Date(2024, 3, 13)],
        [new Date(2024, 3, 10), new Date(2024, 3, 15)],
    )
)

console.log(
    isRangesOverlap(
        [new Date(2024, 3, 9), new Date(2024, 3, 11)],
        [new Date(2024, 3, 10), new Date(2024, 3, 15)],
    )
)