Javascript：从数组中获取连续的天数？

Question

I have an array of ISO dates, ["2019-09-10", "2019-09-14", "2019-09-11", "2019-09-22","2019-09-25"]; I am trying to find the best approach to return an array of objects that are pairs. For example:

let results: [
   {start: 2019-09-10, end: 2019-09-11},
]

I tried using milliseconds to compare but it seems to just return the same day as well, {start: 2019-09-11, end: 2019-09-11}

Answer 1

One way to do this is to first sort the elements by dates, then compare them pairwise to see if they are consecutive. In the example below, I use the date-fns to parse them and make comparing them easier, but you could probably make do without it.

The real key takeaway is sorting the elements, then reducing over them. The reducer function can take more than just the accumulator and the currentValue ; you can also get the index and the array being iterated over. The latter two make it easy to look up the next element, and compare it to see if something should be added to the accumulator .

const addDays = require('date-fns/addDays')
const parse = require('date-fns/parseISO')

const dates = ["2019-09-10", "2019-09-14", "2019-09-11", "2019-09-22","2019-09-25"]

//First, we map them to date objects, and sort the new list.
const sorted = dates.map(d => parse(d)).sort((a,b) => a-b)

//Then we reduce over the entire list, checking pairwise for the dates to be consecutive
const pairs = sorted.reduce((pairs, start, i, dates) => {
  const end = dates[i+1]
  if (addDays(start, 1)-end === 0) pairs.push({start, end})
  return pairs
}, [])