realm-time-zone.js

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// |reftest| skip-if(!this.hasOwnProperty('Intl')||!xulRuntime.shell)

// Don't run in browser because `SpecialPowers.Cu.getJSTestingFunctions()` doesn't

// appear to be able to change time zone in other Realms.

const nsPerMinute = 60 * 1000 * 1000 * 1000;

// Default time zone for jstests is PST8PDT.

const defaultTimeZone = "PST8PDT";

function test(timeZone) {

  // The time zone of the initial global is correct.

  assertEq(getRealmTimeZone(), defaultTimeZone);

  // Create a new global with a different time zone.

  var g = newGlobal({timeZone});

  var initialTimeZone = timeZone ?? defaultTimeZone;

  // Ensure the new global has the expected time zone.

  assertEq(g.getRealmTimeZone(), initialTimeZone);

  // Create a Date object in the new global.

  var d = new g.Date();

  // Call getTimeZoneOffset to fill the local date-time slots in |d|.

  assertEq(

    d.getTimezoneOffset() * nsPerMinute,

    -d.toTemporalInstant().toZonedDateTimeISO(initialTimeZone).offsetNanoseconds

);

  // Change the time zone of the new global.

  g.setRealmTimeZone("Asia/Tokyo");

  // Ensure the new global has the expected time zone.

  assertEq(g.getRealmTimeZone(), "Asia/Tokyo");

  // The time zone of the initial global hasn't changed.

  assertEq(getRealmTimeZone(), defaultTimeZone);

  // Ensure the local date-time slots in |d| don't return stale values.

  assertEq(

    d.getTimezoneOffset() * nsPerMinute,

    -d.toTemporalInstant().toZonedDateTimeISO("Asia/Tokyo").offsetNanoseconds

);

  // Change the time zone of the new global to use the default time zone.

  g.setRealmTimeZone(undefined);

  // Ensure the new global has the expected time zone.

  assertEq(g.getRealmTimeZone(), defaultTimeZone);

  // Ensure the local date-time slots in |d| don't return stale values.

  assertEq(

    d.getTimezoneOffset() * nsPerMinute,

    -d.toTemporalInstant().toZonedDateTimeISO(defaultTimeZone).offsetNanoseconds

);

test();

test("Europe/London");

if (typeof reportCompare === "function")

  reportCompare(true, true);