The Math.atanh() static method returns the inverse hyperbolic tangent of a number. That is,

The flatMap() method of Iterator instances returns a new iterator helper object that takes each element in the original iterator, runs it through a mapping function, and yields elements returned by the mapping function (which are contained in another iterator or iterable).

The find() method of Iterator instances is similar to Array.prototype.find(): it returns the first element produced by the iterator that satisfies the provided testing function. If no values satisfy the testing function, undefined is returned.

The equals() method of Temporal.PlainTime instances returns true if this time is equivalent in value to another time (in a form convertible by Temporal.PlainTime.from()), and false otherwise. They are compared by their time values. It is equivalent to Temporal.PlainTime.compare(this, other) === 0.

The with() method of Temporal.PlainDate instances returns a new Temporal.PlainDate object representing this date 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 date's fields.

The Temporal.ZonedDateTime() constructor creates Temporal.ZonedDateTime objects.

The equals() method of Temporal.PlainDate instances returns true if this date is equivalent in value to another date (in a form convertible by Temporal.PlainDate.from()), and false otherwise. They are compared both by their date values and their calendars, so two dates from different calendars may be considered equal by Temporal.PlainDate.compare() but not by equals().

The day accessor property of Temporal.PlainDateTime instances returns a positive integer representing the 1-based day index in the month of this date, which is the same day number you would see on a calendar. It is calendar-dependent.

The withPlainTime() method of Temporal.PlainDateTime instances returns a new Temporal.PlainDateTime object representing this date-time with the time part entirely replaced by the new time (in a form convertible by Temporal.PlainTime.from())

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