How to sort array by date when some dates are null

Question

So I am trying to sort array of objects by date but I want objects with dates to be priority over objects with null dates.

Example of non sorted array:

[
  {due_date: null},
  {due_date: '03/11/2020'},
  {due_date: '02/10/2020'}
]

And I would like the the array to be in this order once sorted

[
  {due_date: '02/10/2020'},
  {due_date: '03/11/2020'},
  {due_date: null}
]

---

However when I run the array through my script

var firstSort = 'due_date'

return array.sort((a, b) => {
  return new Date(a[this.firstSort]) - new Date(b[this.firstSort])
})

I get this result

[
  {due_date: null},
  {due_date: '02/10/2020'},
  {due_date: '03/11/2020'}
]

How can I compare a null date or exclude it when sorting?

Answer 1

Transform the strings to dates and sort. For the nulls, use date in the distant future so they will sort to the end.

 let dates = [ { due_date: null }, { due_date: '03/11/2020' }, { due_date: '02/10/2020' } ] const distantFuture = new Date(8640000000000000) const firstSort = 'due_date' let sorted = dates.sort((a, b) => { let dateA = a[firstSort] ? new Date(a[firstSort]) : distantFuture let dateB = b[firstSort] ? new Date(b[firstSort]) : distantFuture return dateA.getTime() - dateB.getTime() }) console.log(sorted)

Answer 2

All you have to do is, if indeed excluding is your goal, you filter the array first for all non-null values and then you sort them like so:

var firstSort = 'due_date'

let dates = [
{ due_date: "01/10/2019" },
{ due_date: "10/11/2019" },
{ due_date: "05/09/2019" },
{ due_date: null },
{ due_date: "01/01/2020" },
{ due_date: null },
]

dates.filter(date => date[firstSort] !== null).sort((a, b) => new Date(a[firstSort]) - new Date(b[firstSort]))

That should do the trick :)