问题描述
环境:Win 10 Pro,Chrome 85,luxon 1.25.0
我最终要实现的目标是:在ASP.Net/c#应用程序中,持续向用户显示直到会话超时为止的时间。因为服务器和客户端可能处于不同的时区,所以我需要每个时区的UTC偏移量。客户的偏移量很容易获得。要查找服务器的偏移量(参考下面的代码片段):服务器代码将页面的上次加载时间放入lblLastLoaded中。对象dto接收已解析的日期部分,包括dto.offset,我收集该日期部分应该以分钟表示。后续对luxon.DateTime.fromObject(dto)的调用失败:pst未定义。当我不设置dto.offset时(通过在下面的代码中注释掉4行),pst成功获取服务器时间,但是没有偏移量;看起来luxon使用的是我本地系统的偏移量,它为-7小时。
<script>
function r4onload() {
// Get server time:
var st = document.getElementById('lblLastLoaded').innerHTML;
// Date Time Offset
// st has form YYYY/MM/dd HH:mm:ss -HH:mm
// 1 2
// 012345678901234567890123456
// For Example 2020/09/29 10:31:56 -07:00
let dto = {};
dto.year = Number(st.substring(0,4));
dto.month = Number(st.substring(5,7));
dto.day = Number(st.substring(8,10));
dto.hour = Number(st.substring(11,13));
dto.minute = Number(st.substring(14,16));
var offsetHour = Number(st.substring(20,23)); // works if these 4 lines are commented out
var offsetMinutes = Number(st.substring(24,26)); // works if these 4 lines are commented out
dto.offset = offsetHour * 60 + Math.sign(offsetHour) * offsetMinutes; // works if these 4 lines are commented out
// dto.offset is correctly calculated to -420 minutes // works if these 4 lines are commented out
var pst = luxon.DateTime.fromObject(dto);
// pst is undefined at this point -- why??
// If I do not include anything about offset above (comment out the 4 lines
// containing offsetHours,offsetMinutes,and dto.Offset,then pst comes out like this:
// 2020-09-29T10:31:00.00000-07:00
// i.e.,luxon used the offset -07:00 of my local system,not the one contained in variable st.
document.getElementById('Parsed').innerHTML = pst;
r4startTime();
}
function r4startTime() {
var dt = luxon.DateTime.local();
var h = dt.hour;
var m = dt.minute;
var s = dt.second;
m = r4checkTime(m);
s = r4checkTime(s);
document.getElementById('CurrTime').innerHTML =
h + ":" + m + ":" + s;
var t = setTimeout(r4startTime,2000);
}
function r4checkTime(i) {
if (i < 10) {i = "0" + i}; // add zero in front of numbers < 10
return i;
}
</script>
一个完整的Visual Studio 2017项目DemoLuxon,位于文件Site.Master中,具有上述代码片段:https://1drv.ms/u/s!AvoFL8QrGVaTsQvbaB8-Zh7GdloV?e=ODjZW5
如果上述方法很尴尬,我将感谢您提出更优雅的方法来确定客户端/服务器偏移差异。
解决方法
我设计了以下变通方法,但是原始问题尚未得到解决:
<script>
function r4onload() {
var st = document.getElementById('lblLastLoaded').innerHTML;
// Date Time Offset
// st has form YYYY/MM/dd HH:mm:ss -HH:mm
// 1 2
// 012345678901234567890123456
// For Example 2020/09/29 10:31:56 -07:00
// Transform to ISO format:
st = st.substring(0,4) + '-' + st.substring(5,7) + '-' + st.substring(8,10)
+ 'T' + st.substring(11,19) + ".000" + st.substring(20);
document.getElementById('Xformed').innerHTML = st;
var pst = luxon.DateTime.fromISO(st,{ setZone: true });
document.getElementById('Parsed').innerHTML = pst;
r4startTime();
}
function r4startTime() {
var dt = luxon.DateTime.local();
var h = dt.hour;
var m = dt.minute;
var s = dt.second;
m = r4checkTime(m);
s = r4checkTime(s);
document.getElementById('CurrTime').innerHTML =
h + ":" + m + ":" + s;
var t = setTimeout(r4startTime,2000);
}
function r4checkTime(i) {
if (i < 10) {i = "0" + i}; // add zero in front of numbers < 10
return i;
}
</script>
,即首先将日期时间输入ISO格式,然后使用luxon.DateTime.fromISO。变量pst获取正确的日期时间值,包括偏移量。带有偏移的luxon.DateTime.fromObject的问题仍未解决。