Temporal.ZonedDateTime.compare()

The Temporal.ZonedDateTime.compare() static method returns a number (-1, 0, or 1) indicating whether the first date-time comes before, is the same as, or comes after the second date-time. It is equivalent to comparing the {{jsxref("Temporal/ZonedDateTime/epochNanoseconds", "epochNanoseconds")}} of the two date-times.

Syntax#

Temporal.ZonedDateTime.compare(dateTime1, dateTime2)

Parameters#

• dateTime1
• : A string, an object, or a {{jsxref("Temporal.ZonedDateTime")}} instance representing the first date-time to compare. It is converted to a Temporal.ZonedDateTime object using the same algorithm as {{jsxref("Temporal/ZonedDateTime/from", "Temporal.ZonedDateTime.from()")}}.
• dateTime2
• : The second date-time to compare, converted to a Temporal.ZonedDateTime object using the same algorithm as dateTime1.

Return value#

Returns -1 if dateTime1 comes before dateTime2, 0 if they are the same, and 1 if dateTime1 comes after dateTime2. They are compared by their underlying instant values, ignoring their calendars or time zones.

Examples#

Using Temporal.ZonedDateTime.compare()#

const dt1 = Temporal.ZonedDateTime.from("2021-08-01T01:00:00[Europe/London]");
const dt2 = Temporal.ZonedDateTime.from("2021-08-02T00:00:00[Europe/London]");
console.log(Temporal.ZonedDateTime.compare(dt1, dt2)); // -1

const dt3 = Temporal.ZonedDateTime.from("2021-08-01T00:00:00[Europe/London]");
console.log(Temporal.ZonedDateTime.compare(dt1, dt3)); // 1

Sorting an array of date-times#

The purpose of this compare() function is to act as a comparator to be passed to {{jsxref("Array.prototype.sort()")}} and related functions.

const dateTimes = [
  Temporal.ZonedDateTime.from("2021-08-01T00:00:00[America/New_York]"),
  Temporal.ZonedDateTime.from("2021-08-01T00:00:00[Asia/Hong_Kong]"),
  Temporal.ZonedDateTime.from("2021-08-01T00:00:00[Europe/London]"),
];

dateTimes.sort(Temporal.ZonedDateTime.compare);
console.log(dateTimes.map((d) => d.toString()));
// [ "2021-08-01T00:00:00+08:00[Asia/Hong_Kong]", "2021-08-01T00:00:00+01:00[Europe/London]", "2021-08-01T00:00:00-04:00[America/New_York]" ]

Note that they are compared by their instant values. In the very rare case where you want to compare them by their wall-clock times, convert them to PlainDateTime first.

const dateTimes = [
  Temporal.ZonedDateTime.from("2021-08-01T00:00:00[America/New_York]"),
  Temporal.ZonedDateTime.from("2021-08-01T00:00:00[Asia/Hong_Kong]"),
  Temporal.ZonedDateTime.from("2021-08-01T00:00:00[Europe/London]"),
];

dateTimes.sort((a, b) =>
  Temporal.PlainDateTime.compare(a.toPlainDateTime(), b.toPlainDateTime()),
);
console.log(dateTimes.map((d) => d.toString()));
// [ "2021-08-01T00:00:00-04:00[America/New_York]", "2021-08-01T00:00:00+08:00[Asia/Hong_Kong]", "2021-08-01T00:00:00+01:00[Europe/London]" ]

Specifications#

{{Specifications}}

Browser compatibility#

{{Compat}}

See also#

• {{jsxref("Temporal.ZonedDateTime")}}
• {{jsxref("Temporal/ZonedDateTime/equals", "Temporal.ZonedDateTime.prototype.equals()")}}