The Symbol.species static data property represents the well-known symbol Symbol.species. Methods that create copies of an object may look up this symbol on the object for the constructor function to use when creating the copy.

# Contributors by commit history https://github.com/mdn/content/commits/main/files/en-us/web/javascript/reference/global_objects/symbol/index.md # Original Wiki contributors fscholz wbamberg ddbeck...

The Symbol.unscopables static data property represents the well-known symbol Symbol.unscopables. The with statement looks up this symbol on the scope object for a property containing a collection of properties that should not become bindings within the with environment.

The WeakSet() constructor creates WeakSet objects.

The Object.freeze() static method freezes an object. Freezing an object prevents extensions and makes existing properties non-writable and non-configurable. A frozen object can no longer be changed: new properties cannot be added, existing properties cannot be removed, their enumerability, configurability, writability, or value cannot be changed, and the object's prototype cannot be re-assigned. freeze() returns the same object that was passed in.

The until() method of Temporal.PlainTime instances returns a new Temporal.Duration object representing the duration from this time to another time (in a form convertible by Temporal.PlainTime.from()). The duration is positive if the other time is after this time, and negative if before.

The eraYear accessor property of Temporal.PlainDate instances returns a non-negative integer representing the year of this date within the era, or undefined if the calendar does not use eras (e.g., ISO 8601). The year index usually starts from 1 (more common) or 0, and years in an era can decrease with time (e.g., Gregorian BCE). era and eraYear together uniquely identify a year in a calendar, in the same way that year does. It is calendar-dependent.

The Temporal.Instant.fromEpochMilliseconds() static method creates a new Temporal.Instant object from the number of milliseconds since the Unix epoch (midnight at the beginning of January 1, 1970, UTC).

The with() method of Temporal.PlainTime instances returns a new Temporal.PlainTime object representing this time with some fields replaced by new values. Because all Temporal objects are designed to be immutable, this method essentially functions as the setter for the time's fields.

The monthCode accessor property of Temporal.PlainYearMonth instances returns a calendar-specific string representing the month of this year-month. It is calendar-dependent.