CONSECUTIVE_DATES

/**
* Calculates the maximimun consecutive dates.
*
* @param {A1:A5} range Input range.
* @return {number} result.
* @customfunction
*/
function CONSECUTIVE_DATES(range) {
  if (!Array.isArray(range)) {
    throw new Error('No range is givin');
  } else if (range[0].length > 1) {
    throw new Error('Only supports single columns')
  }

  const log = []
  let max = 1;
  let counter = 1;

  range.flat().forEach((date, i, array) => {
    const nextDate = array[i + 1]
    if (date != "" && nextDate != "") {

      if (isValid(date) == false || isValid(nextDate) == false) {
        throw new Error('Input is not of type date')
      };

      const difference = nextDate.getTime() - date.getTime()


      if (difference === 86400000) {
        counter++
      } else if (counter > max) {
        max = counter
        counter = 1
      } else {
        counter = 1
      }
    }
  })

  console.log(log)
  return (counter > max) ? counter : max
}

function isValid(date) {
  return date.getTime() === date.getTime()
}