javascript - 如何在 JavaScript 中从 IANA 时区代码获取时区偏移量？

Question

我有IANA时区代码，如“亚洲/加尔各答”，我需要在 JavaScript 中获取时区偏移量，如 -330。我无法获得时区偏移，我们将不胜感激。

Answer 1

使用 native Date.toLocaleString API:

function timeZoneOffsetInMinutes(ianaTimeZone) {
  const now = new Date();
  now.setSeconds(0, 0);

  // Format current time in `ianaTimeZone` as `M/DD/YYYY, HH:MM:SS`:
  const tzDateString = now.toLocaleString('en-US', {
    timeZone: ianaTimeZone,
    hourCycle: 'h23',
  });

  // Parse formatted date string:
  const match = /(\d+)\/(\d+)\/(\d+), (\d+):(\d+)/.exec(tzDateString);
  const [_, month, day, year, hour, min] = match.map(Number);

  // Change date string's time zone to UTC and get timestamp:
  const tzTime = Date.UTC(year, month - 1, day, hour, min);

  // Return the offset between UTC and target time zone:
  return Math.floor((tzTime - now.getTime()) / (1000 * 60));
}