FindLast and FindLastIndex
While the find method provides the first matching element in a search, sometimes we want the final match, instead. findLast and findLastIndex help us do this.
Change Arrays in Copies
Improved array techniques enable alterations to an array while preserving the original. Instead of directly modifying the array, you generate a copy and make the changes. This maintains the array's integrity while facilitating work with altered versions.
Symbols as WeakMap Key
Symbols are unique and immutable, making them good keys for data storage, unlikely to cause conflicts. This is an improvement from using objects as keys, which can lead to issues like memory leaks or unexpected behavior due to their referential nature.