In which cases should Set be used instead of Array?

Set should be used when the following aspects are important:

• Uniqueness of elements: Set by its nature does not allow duplicate elements. If you need a collection of unique values, Array will require additional logic to filter them.
• High performance of membership operations (checking for presence): Checking whether a Set contains a specific element has an average complexity of O(1) (amortized), whereas for Array it is O(n).
• High performance of insertion and deletion operations: Inserting and removing elements by value in a Set also typically have a complexity close to O(1), whereas for Array it can reach O(n) in case of insertion/removal not at the end.
• No need to maintain the order of elements: Set does not guarantee any specific order of elements. If order is important, use Array.

Typical scenarios for using Set:

• Storing a set of unique identifiers.
• Filtering duplicates from a collection.
• Efficiently performing set operations such as union, intersection, and difference.
• Fast checking of element presence in a collection.

Example of obtaining unique elements from an array using Set:

let numbers = [1, 2, 3, 2, 4, 1, 5]
let uniqueNumbers = Set(numbers) // {1, 2, 3, 4, 5} - order is not guaranteed