ECMAScript 2022: Ergonomic brand check for private fields

ECMAScript 2022 provides a simpler way to check if an object has a given private field using the 'in' operator.

ECMAScript 2022 introduces at() method in Array, String, TypedArray

The at() method takes an integer value and returns the element at that index. It allows both positive and negative integers. Negative integers denote counting back from the last item in the array.