问题
I have recently discovered that there is a new extension to JavaScript. This adds several features to the Date object in the toLocaleString, toLocaleDateString and toLocaleTimeString functions. Reference here.
I am particularly interested in the timeZone option, that supports IANA/Olson time zones, such as America/New_York or Europe/London. This is currently only supported in Google Chrome.
Previous advice was that to work in JavaScript with any other time zone than UTC or your own local time zone, one had to use a library. But now, it appears that this is starting to be incorporated directly into the browser. So now you can do this:
new Date().toLocaleString("en-US", {timeZone: "America/New_York"})
// output: "7/4/2013 5:15:45 PM"
Or:
new Date().toLocaleString("en-NZ", {timeZone: "Pacific/Chatham",
timeZoneName: "long"})
// output: "7/5/2013 9:59:52 AM GMT+12:45"
Or:
new Date().toLocaleString("en-GB", {timeZone: "Europe/London",
timeZoneName: "short"})
// output: "4/7/2013 22:18:57 United Kingdom Time"
// (strange time zone name, but ok)
This is very cool, but I have a few questions:
- Is this part of a new standard? Perhaps buried somewhere in ECMAScript 6? Or is it just something custom to Chrome?
- Why just Google Chrome? Is it supported anywhere else? Are there plans to supported it anywhere else?
- I checked node.js, which uses Chrome's JavaScript runtime, but it doesn't work there. Why not?
- Is the time zone data accessible in any other way than the functions I listed? If only available when formatting strings, then doing any calculations based on the results may be difficult.
This is focused on output, but how would I use it for input? Is there a way to pass the time zone in the constructor to the
Dateobject? I tried the following:// parsing it with a date and time new Date("2013-01-01 12:34:56 America/New_York") // passing it as a named option new Date(2013,0,1,12,34,56,{timeZone:"America/New_York"})Neither worked. I couldn't find anything in the specs, so I don't think this exists (yet), but please tell me if I am wrong.
The issue described in this post, created by a flaw in the ECMAScript 5 spec, still affects the output, even when the correct data is in the TZDB. How is it that both old and new implementations are coexisting? One would think it would be all the old way, or all the new way. For example, with my computer's time zone set to US Eastern Time:
new Date(2004,10,7,0,0).toLocaleString("en-US",{timeZone:"America/New_York"})returns
"11/6/2004 11:00:00 PM". It should return midnight, since I started at midnight and my local time zone matches the output time zone. But it places the provided input date at the wrong UTC point due to the ES5 issue.Can I expect that as IANA releases updates to the TZDB that Google will push Chrome updates that contain the changes?
回答1:
update
There is pretty extensive write-up about the API here
Is this part of a new standard? Perhaps buried somewhere in ECMAScript 6? Or is it just something custom to Chrome?
Yes, these are part of the ECMAScript Internationalization API. It is implemented separate from ECMAScript, but the requirement of implementing ECMAScript Internationalization API is to first have correct implementation of ECMAScript 5.1
Why just Google Chrome? Is it supported anywhere else? Are there plans to supported it anywhere else?
For the recent years, Google Chrome has mostly been first to implement new features. Mozilla is more conservative, still for example discussing whether to implement the download attribute of a elements. It is now available in IE11 Beta and Opera too. It will be available in Firefox 25.
I checked node.js, which uses Chrome's JavaScript runtime, but it doesn't work there. Why not?
node.js just uses the same engine, which is a separate project from the Google Chrome browser. The engine just implements Ecmascript 5.1. This is an extension node.js would have to implement separately right now. It will become available in V8 in Q3 so probably a bit after that you can use it in node.js.
This is focused on output, but how would I use it for input? Is there a way to pass the time zone in the constructor to the Date object? I tried the following:
There is nothing about inputting dates in the specification. I personally cannot see how this would be useful, you are doing it wrong if you are not transmitting UTC timestamps because something like "2013-01-01 12:34:56 America/New_York" is ambiguous during transitions from DST to standard time.
The issue described in this post, created by a flaw in the ECMAScript 5 spec, still affects the output, even when the correct data is in the TZDB.
This is input issue, not output. Again, constructing a date with local timezone that you cannot influence or detect is doing it wrong. Use the timestamp constructor overload or Date.UTC.
Can I expect that as IANA releases updates to the TZDB that Google will push Chrome updates that contain the changes?
Nothing in the spec but I think it will be reasonable to expect that the rules are not too much behind.
回答2:
Is this part of a new standard? Perhaps buried somewhere in ECMAScript 6? Or is it just something custom to Chrome?
Indeed it is part of the new ECMA-402 standard. The standard is very difficult to read, but there is this friendly introduction.
Why just Google Chrome? Is it supported anywhere else? Are there plans to supported it anywhere else?
MDN has a list of supporting browsers. According to Bug 853301 it will be available in Firefox 25.
I checked node.js, which uses Chrome's JavaScript runtime, but it doesn't work there. Why not?
Possible reasons are many; it is not up to the current code base, or it would make the node.js bigger and slower (the previous bug tracker entry from Mozilla indicates that the timezone data increased the download size of Firefox by 10 %, and caused the I/O to increase substantially during browser start up.
Is the time zone data accessible in any other way than the functions I listed? If only
available when formatting strings, then doing any calculations based on the results may be difficult.
Seems that it is not available. Furthermore, the Intl API primer talks that only UTC and local time zone are absolutely required to be supported.
This is focused on output, but how would I use it for input? Is there a way to pass the time zone in the constructor to the Date object? I tried the following:
The Intl API only speaks about date/time formatting, string collations and number formatting. The datetime formatting not only supports the Gregorian calendar but also many kinds of other calendars, lunar, lunisolar and so forth.
The issue described in this post, created by a flaw in the ECMAScript 5 spec, still affects the output, even when the correct data is in the TZDB. How is it that both old and new implementations are coexisting? One would think it would be all the old way, or all the new way. For example, with my computer's time zone set to US Eastern Time:
new Date(2004,10,7,0,0).toLocaleString("en-US",{timeZone:"America/New_York"})
returns "11/6/2004 11:00:00 PM". It should return midnight, since I started at midnight and > my local time zone matches the output time zone. But it places the provided input date at the > wrong UTC point due to the ES5 issue.
The reason for that is that ES5 mandates that the input to new Date be calculated using the current DST and offset, that is it is America/New York but with EDT timezone, even though Nov 6 is not in EDT. Obviously as this is so specified, then it cannot be changed. However, as Chrome is using the TZDB to do the conversion from the bare UTC point-in-time value to the America/New York tz, it then does consider the time as being in EST.
Can I expect that as IANA releases updates to the TZDB that Google will push Chrome updates that contain the changes?
I'd believe so
来源：https://stackoverflow.com/questions/17478086/chrome-timezone-option-to-date-tolocalestring