如何从 javascript 中的字符串获取时区偏移量？

Question

I have a string 2021-04-07T13:51:39.664+11:00 which I use to create a Date object: d = new Date('2021-04-07T13:51:39.664+03:00') .

After that, d is an instance to represent the date time. Now I'd like to get the timezone offset from d , but d.getTimezoneOffset() always return local timezone offset which is -600 in my case. How can I get the timezone offset from the string? Does it get lost when I build the date instance? Do I have to parse the string to get it?

If I have a date object, how can I generate a string with the offset at the end: 2021-04-07T13:51:39.664+03:00 ? toISOString() only generate UTC time.

I know moment is a good date library but I don't want to add this dependency since it is too large.

Answer 1

 function dateZ(dateString) { var _date = dateString.substring(0, 23); var _offset = dateString.substring(23); var _dateValue = new Date(dateString); function offset(value) { if (value) { _offset = value; _dateValue = new Date(toString()); } return _offset; } function date(value) { if (value) { _date = value; _dateValue = new Date(toString()); } return _dateValue; } function toString() { return `${_date}${_offset}` } return { offset, date, toString }; } var d = dateZ('2021-04-07T13:51:39.664+03:00'); console.log(d.date(), d.offset(), d.toString()); d.offset('+05:30'); console.log(d.date(), d.offset(), d.toString());

Answer 2

This is probably not the best possible approach, but it is portable and quite useful if you are in control of the application environment.

 friendlyDate = function( x ){ var label = "Day Month Date Year Time Offset".split(" "), d = x? new Date(x): new Date(), s = ( d + "" ).split( / / ); s.length = label.length; for( var x in s )s[ label[ x ] ] = s[ x ]; s.length = 0; return s } /**/ dte = friendlyDate(); for(var x in dte)console.log(x + ": "+ dte[x]);

ps: you might need to readjust\rearrange the labels for certain targeted browsers. [Not all browser vendor\version date string representations are returned equal;)]

Answer 3

How to initialize a JavaScript Date to a particular time zone

There is no time zone or string format stored in the Date object itself.

Seems like either string parsing or a library (there are lighter-weight ones than moment if you're interested).