給定一個元素都為yyyy/mm/dd的array，將其連續的日期使用`${start}-{end}`的方式串在一起

foramt_date_array.js

<script>
  function formatDateRange(dateArray) {
    if (dateArray.length < 2) {
      return dateArray
    }

    const result = dateArray.reduce((acc, curDateStr, index, array) => {
      const curDate = new Date(curDateStr)

      if (acc.rangeEnd && curDate === acc.rangeEnd) {
        return acc
      }

      if (index+1 <= array.length) {
        const nextDate = new Date(array[index+1])
        const endDate = curDate.setDate(curDate.getDate()+1)
        if (endDate - nextDate === 0) {
          // 連續
          if (acc.rangeStart === null) {
            acc.rangeStart = curDateStr
          }
          acc.rangeEnd = array[index+1]
          return acc
        }
      }

      // 不連續
      if (acc.rangeEnd !== null) {
        // 放入之前連續時的資料
        acc.formatted.push(`${acc.rangeStart}-${acc.rangeEnd}`)
        acc.rangeStart = null
        acc.rangeEnd = null
      } else {
        acc.formatted.push(curDateStr)
      }

      return acc;
    }, {
      rangeStart: null,
      rangeEnd: null,
      formatted: []
    })

    return result.formatted
  }

  for (const testData of [
    ['2023/09/01'],
    [
      '2023/09/01',
      '2023/09/08',
      '2023/09/02',
      '2023/09/12',
      '2023/09/03',
      '2023/09/04',
    ],
    [
      '2023/09/30',
      '2023/10/1',
      '2023/10/5',
      '2023/10/2',
      '2023/10/6',

      '2023/12/31',
      '2024/1/1',
      '2024/1/5',
      '2024/1/2',
    ],
  ]){
    testData.sort((b, a)=>{
      const dateA = new Date(a)
      const dateB = new Date(b)
      return dateB - dateA
    })

    const formattedArray = formatDateRange(testData)
    console.log(formattedArray)
  }

  /*
  Output:
  ['2023/09/01']
  ['2023/09/01-2023/09/04', '2023/09/08', '2023/09/12']
  ['2023/09/30-2023/10/2', '2023/10/5-2023/10/6', '2023/12/31-2024/1/2', '2024/1/5']
  **/
</script>