adding previousDay and its variations

[LucasHFS]

[WIP] Implements #2507 request, and similar functions.

[tan75]

Hi @LucasHFS
thanks a mill!
I linked the mentioned issue to this PR and marked it as WIP until it gets approval.
Can you please have a look into this test as it is failing?

  41 |   it('returns the previous Tuesday given the Saturday after it', function () {
    > 42 |     assert.deepStrictEqual(

if you prefer to run tests locally you can do
yarn test

Many thanks!

[fturmel]

Minor stuff, but you have a little typo in your tests (previours instead of previous).

Could I also propose a simpler and faster (by about 50%) implementation for previousDay? nextDay could be refactored using the same approach as well.

export default function previousDay(dirtyDate: Date | number, day: Day): Date {
  requiredArgs(2, arguments)

  const date = toDate(dirtyDate)

  let delta = getDay(date) - day
  if (delta <= 0) delta += 7

  return subDays(date, delta)
}

[LucasHFS]

Sure, tomorrow I'll work on this.

[fturmel]

@LucasHFS @tan75

There's already a PR for the nextDay optimization that has been approved (#2524). Should the change be reverted here or should I close 2524?

[tan75]

@LucasHFS @tan75

There's already a PR for the nextDay optimization that has been approved (#2524). Should the change be reverted here or should I close 2524?

This PR 2524 will be included in our next release hopefully soon enough.
And #2522 can be added after. If any conflicts - we will fix it!

Thanks guys! 👍 🥇

[tan75]

Thanks a lot for your contribution! 🚀

[fturmel]

Just had a look again at this PR and I think there's no need to convert the date argument using toDate before passing it to previousDay. This optimization applies to all the next* functions as well (nextMonday, etc).

ex:

export default function previousThursday(date: Date | number): Date {
  requiredArgs(1, arguments)
  return previousDay(toDate(date), 4)
}

could simply be:

export default function previousThursday(date: Date | number): Date {
  requiredArgs(1, arguments)
  return previousDay(date, 4)
}

[tan75]

@fturmel this totally makes sense! Thank you!
Will need to change the next* ones in a separate PR.