The at() method of Array instances takes an integer value and returns the item at that index, allowing for positive and negative integers. Negative integers count back from the last item in the array.

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

The Number.NEGATIVE_INFINITY static data property represents the negative Infinity value.

The Number.isFinite() static method determines whether the passed value is a finite number — that is, it checks that a given value is a number, and the number is neither positive Infinity, negative Infinity, nor NaN.

The Math.floor() static method always rounds down and returns the largest integer less than or equal to a given number.

The Math.abs() static method returns the absolute value of a number.

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

The format() method of Intl.DateTimeFormat instances formats a date according to the locale and formatting options of this Intl.DateTimeFormat object.

The resolvedOptions() method of Intl.Collator instances returns a new object with properties reflecting the locale and collation options computed during initialization of this collator object.

The compare() method of Intl.Collator instances compares two strings according to the sort order of this collator object.