What would be the proper way to filter by date

Question

I have an array of objects with date strings formatted as so 2019-03-22T13:36:18.333Z

I am curious what the best course of action would be to sort these by past day, past week, past month and past year.

I was thinking of just splitting at the T then splitting again at the -

I was also considering putting the date into the Date object and figuring it out that way.

What would be the most dynamic? Most efficient? etc.

const dates = [
  {created_at: '2019-03-22T13:36:18.333Z'}
  {created_at: '2019-05-22T13:36:18.333Z'}
  {created_at: '2019-03-23T13:36:18.333Z'}
  {created_at: '2019-03-24T13:36:18.333Z'}
  {created_at: '2019-01-22T13:36:18.333Z'}
]

const spliteDate = (date, splitBy) => {
  if(splitBy = 'day'){
    return date.split("T")[0].split("-")[1]
  } else if(splitBy = 'month') {
    return date.split("T")[0].split("-")[2]
  } else if(splitBy = 'year') {
    return date.split("T")[0].split("-")[0]
  }
}

dates.filter(date => {
  return splitDate(date, 'month') === Date.now().getMonth()
}

Something along these lines

Answer 1

It is probably the easiest to convert the strings to Date objects

For instance, you have an array of dates in string format:

const arr = ['2019-03-22T13:36:18.333Z', '2019-03-28T16:36:18.333Z', '2015-05-21T16:36:18.333Z'];

Looking at your question, if you would like to filter it by a certain date, it is definitely much shorter and efficient to do this:

const filterByDate = dateFilter => arr.filter(date => new Date(date).getDate() < dateFilter);

filterByDate(25);
// result [ '2019-03-22T13:36:18.333Z', '2019-05-21T16:36:18.333Z' ]

And, if you require multiple filters, for instance filter by date AND year,

const filterByDateAndYear = (dateFilter, yearFilter) => arr.filter(date => (new Date(date).getDate() < dateFilter) && (new Date(date).getFullYear() < yearFilter));

filterByDateAndYear(25, 2018);

//result [ '2015-05-21T16:36:18.333Z' ]