Set

Summary

A built-in collection that stores only unique values — the simplest way to deduplicate an array or track membership in JS. `Set` expresses membership and uniqueness directly, which often makes deduplication and lookup-oriented logic clearer than repeatedly scanning an array.

• 1Deduplicate an array using `[...new Set(array)]`. Validate your understanding by applying it in a small practical example.
• 2Use a `Set` to track which items a user has already seen or clicked. Verify the behavior with realistic data and handle the failure or empty state as well.
• 3Compare `Set.has()` conceptually against `Array.includes()` for large lists.