Date.prototype.toLocaleTimeString() 中的 hourCycle 选项有什么区别

Question

toLocaleTimeString() 的 MDN 文档指出 hourCycle 和 hc 选项有四个可能的值："h11"、"h12"、"h23"、& "h24".

两个可能的值让我觉得非常明显（即 "h12" 和 "h24"），但是另外两个，我不知道它们是做什么的，我的 duckduckfoo/googlefoo 是让我失望！

"h11" 和 "h23" 值代表什么？

我最好的猜测是它们是 0 和 "h12" 和 "h24" 的 1 派生的某种类型，但基础日期戳仍然相同，并且记录的值是相同的，所以如果是这样，区别在哪里？

这应该在 MDN's toLocalTimeString page or ECMAScript's toLocalTimeString page 上记录，或者至少链接到，但事实并非如此。它也确实给我留下了深刻的印象，因为它应该很容易弄清楚，但我没有看到其中的区别，它现在在我的皮肤下爬行！

const now = new Date();
console.log('hourCycle: h11', now.toLocaleTimeString('en-US', { hourCycle: 'h11' }))
console.log('hourCycle: h12', now.toLocaleTimeString('en-US', { hourCycle: 'h12' }))
console.log('hourCycle: h23', now.toLocaleTimeString('en-US', { hourCycle: 'h23' }))
console.log('hourCycle: h24', now.toLocaleTimeString('en-US', { hourCycle: 'h24' }))

Answer 1

我发现dateStyle and timeStyle options for Intl.DateTimeFormat的提案说：

[[HourCycle]] is a String value indicating whether the 12-hour format ("h11", "h12") or the 24-hour format ("h23", "h24") should be used. "h11" and "h23" start with hour 0 and go up to 11 and 23 respectively. "h12" and "h24" start with hour 1 and go up to 12 and 24. [[HourCycle]] is only used when [[Hour]] is not undefined.

英式或美式可能更喜欢h12:

› new Date(2019,4,1,12,0,0).toLocaleString('en-US', { hourCycle: 'h12' })
‹ "5/1/2019, 12:00:00 PM"
› new Date(2019,4,1,12,0,0).toLocaleString('en-US', { hourCycle: 'h11' })
‹ "5/1/2019, 0:00:00 PM"

h24 必须谨慎使用。如果日期部分是前一天的值就好了。

› new Date(2019,4,1,0,59,59).toLocaleString('ja-JP', { hourCycle: 'h23' })
‹ "2019/5/1 0:59:59"
› new Date(2019,4,1,0,59,59).toLocaleString('ja-JP', { hourCycle: 'h24' })
‹ "2019/5/1 24:59:59"

Compatibility table in MDN 说 Firefox 58 和 Edge 支持这个。

Answer 2

我同意目前很难找到关于 hourCycle 值的 MDN 文档，但我在这里找到了它们：

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Locale/hourCycle

Web technology for developers > JavaScript > JavaScript reference > Standard built-in objects > Intl.Locale > Intl.Locale.prototype.hourCycle

[…]

h12: Hour system using 1–12; corresponds to 'h' in patterns. The 12 hour clock, with midnight starting at 12:00 am.

h23: Hour system using 0–23; corresponds to 'H' in patterns. The 24 hour clock, with midnight starting at 0:00.

h11: Hour system using 0–11; corresponds to 'K' in patterns. The 12 hour clock, with midnight starting at 0:00 am.

h24: Hour system using 1–24; corresponds to 'k' in pattern. The 24 hour clock, with midnight starting at 24:00.

Date.prototype.toLocaleTimeString() 中的 hourCycle 选项有什么区别

What are the differences between the hourCycle options in Date.prototype.toLocaleTimeString()

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