The findLast() method of Array instances iterates the array in reverse order and returns the value of the first element that satisfies the provided testing function. If no elements satisfy the testing function, undefined is returned.

The keys() method of Array instances returns a new array iterator object that contains the keys for each index in the array.

The set() method of Map instances adds or updates an entry in this map with a specified key and a value.

The entries() method of Map instances returns a new map iterator object that contains the [key, value] pairs for each element in this map in insertion order.

The length data property of an Array instance represents the number of elements in that array. The value is an unsigned, 32-bit integer that is always numerically greater than the highest index in the array.

The catch() method of Promise instances schedules a function to be called when the promise is rejected. It immediately returns another Promise object, allowing you to chain calls to other promise methods. It is a shortcut for then(undefined, onRejected).

The then() method of Promise instances takes up to two arguments: callback functions for the fulfilled and rejected cases of the Promise. It stores the callbacks within the promise it is called on and immediately returns another Promise object, allowing you to chain calls to other promise methods.

The handler.defineProperty() method is a trap for the [[DefineOwnProperty]] object internal method, which is used by operations such as Object.defineProperty().

The toArray() method of Iterator instances creates a new Array instance populated with the elements yielded from the iterator.

The reduce() method of Iterator instances is similar to Array.prototype.reduce: it executes a user-supplied "reducer" callback function on each element produced by the iterator, passing in the return value from the calculation on the preceding element. The final result of running the reducer across all elements is a single value.