refactor:(std/datetime) weekOfYear: Use constants, improve readability

[jsejcksn]

Related issue: #6601
Related PR: #6659

This PR improves readability for code and documentation.

I noticed the use of literal millisecond and integer values, and an opportunity to remove some comments and improve code readability, so I refactored it, using constants instead of the literals.

The new tests are sourced from moment.js.

[CLAassistant]

All committers have signed the CLA.

[jsejcksn]

While working on this, I felt a pull to add a currentWeekOfYear function to mirror the currentDayOfYear function. However, I'm not sure what real value that would add, since it's a very simple abstraction—literally:

weekOfYear(new Date());

This made me wonder further: what is the defined purpose of std/datetime? These kinds of functions already exist elsewhere in dedicated libraries like date-fns, moment, luxon, etc. However, the style guide states Do not depend on external code, so is the aim to re-invent the wheel or copy from them?

[jsejcksn]

Should these be exported, or kept private unless/until needed? I didn't see any guidelines about conditions for exporting, keeping exports to a minimal, etc.

[timreichen]

I suggested to remove the currentDayOfYear in that issue.

As for the purpose of std/datetime: I think a clear definition has to be worked out still, but I think it is a good addition as a std library. In my view the module has theses purposes at the moment:

• provide commonly used functions related to date and time
• provide datetime parser and formatter

I think some 3rd party libraries do the one, some the other.
I did a PR to add a generic parser and a formatter. In a sense some features are reinventing the wheel (like parser and formatter) but the attention lies to provide compatibility with Intl.
Also this module will likely change once this proposal is at stage 4.

[jsejcksn]

Temporal looks like a step forward. 🧗

@bartlomieju Any feedback about exports?

[jsejcksn]

Re: fmt

I ran:

./tools/format.py

from the repo root directory, but it exited with an error. I don't remember the exact error, but I'm wondering if that step can be added to the repo actions, since I'm not the first to run into this problem.

Related: Is deno fmt equivalent to the python formatter for TS/JS files?

[bartlomieju]

This made me wonder further: what is the defined purpose of std/datetime? These kinds of functions already exist elsewhere in dedicated libraries like date-fns, moment, luxon, etc. However, the style guide states Do not depend on external code, so is the aim to re-invent the wheel or copy from them?

The purpose for datetime/ hasn't really been defined. It's definitely useful to have date manipulation utilities in standard library, but the scope hasn't been set. Before stabilizing std/ we'll reevaluate each module.

from the repo root directory, but it exited with an error. I don't remember the exact error, but I'm wondering if that step can be added to the repo actions, since I'm not the first to run into this problem.

This issue should be resolved when #6682 lands.

Related: Is deno fmt equivalent to the python formatter for TS/JS files?

No, it's not, current repository uses prettier.

[ry]

LGTM - thanks!