Determine whether two dates coincide

analyze

First of all, there are two main scenarios for overlapping date segments:

1. date_segment contains date_segment2 ;
2. Date segment 2 contains date segment 1 .

The translation of the above is that
if the start date of date segment 2 is after the start date of date segment 1 , date segment 1 may include date segment 2 ;
if the start date of date segment 2 is before the start date of date segment 1 , then It is possible that date segment 2 contains date segment 1 .

Then we assume that the start date and end date of date segment 1 are A and B respectively, and the start date and end date of date segment 2 are X and Y respectively. Based on date segment 1 , first list the start date of date segment 1 <= In the case of the start date of date segment 2 .

---

日期段1 开始日 = 日期段2 开始日：

1. 日期段2 开始日 = 日期段1 开始日
A------B
XY
X--Y
X------Y
X----------Y



日期段1 开始日 < 日期段2 开始日：

2. 日期段1 开始日 < 日期段2 开始日 < 日期段1 结束日
A------B
  XY
  X--Y
  X----Y
  X-------Y

3. 日期段2 开始日 = 日期段1 结束日
A------B
       XY
       X---Y

3. 日期段2 开始日 > 日期段1 结束日
A------B
         XY
         X---Y

---

Next, based on date segment 1 , list the cases where the start date of date segment 1 > date segment 2 .
(It can also be changed to date segment 2 as the benchmark, and A, B, X, and Y in the above analysis can be exchanged)

---

日期段1 开始日 > 日期段2 开始日：

4. 日期段2 结束日 < 日期段1 开始日
X---Y
      A------B

5. 日期段2 结束日 = 日期段1 开始日
X-----Y
      A------B

6. 日期段1 开始日 > 日期段2 结束日 > 日期段1 结束日
X--------Y
      A------B

7. 日期段2 结束日 = 日期段1 结束日
X------------Y
      A------B

8. 日期段2 结束日 > 日期段1 结束日
X---------------Y
      A------B

in conclusion

By observing the above analysis, it is found that the segment dates of only two scenarios do not coincide:

1. Type 3: Start date of date range 1 < start date of date range 2 , and start date of date range 2 > end date of date range 1
2. Type 4: start date of date range 1 > start date of date range 2 , and end date of date range 2 < start date of date range 1

Then, other situations outside these two scenarios are judged as duplication.

the code

function isDuplicateDatePeriod(currPeriod = [], otherPeriod = []) {
    
    
  const [currStartDay, currEndDay] = currPeriod;
  const [otherStartDay, otherEndDay] = otherPeriod;
  if (!currStartDay || !currEndDay || !otherStartDay || !otherEndDay) {
    
    
    // 日期不完整，认为不重复
    return false;
  }
  const currStartTime = new Date(currStartDay).getTime();
  const currEndTime = new Date(currEndDay).getTime();
  const otherStartTime = new Date(otherStartDay).getTime();
  const otherEndTime = new Date(otherEndDay).getTime();

  if (otherStartTime > currStartTime) {
    
    
    // 其他日期段开始日期大于当前日期段开始日日期，那么其他日期段开始日期小于等于当前日期段结束日则为重复
    return otherStartTime <= currEndTime;
  } else if (otherStartTime < currStartTime) {
    
    
    // 其他日期段开始日期小于当前开始日期，那么其他日期段结束日期大于等于当前日期段开始日期则为重复
    return otherEndTime >= currStartTime;
  } else {
    
    
    // 其他日期段开始日期=当前日期段开始日期，一定重复
    return true
  }
}