Map

Summary

A built-in key-value collection (like an object) but with keys of any type, guaranteed insertion order, and a cleaner API (`.get`, `.set`, `.has`). `Map` is especially useful when keys are not limited to strings or when explicit collection operations and reliable insertion order make the intent clearer than a plain object.

• 1Build a small cache using a `Map` instead of a plain object. Keep the first version small, then add one improvement after the core behavior works.
• 2Try using an object (not just a string) as a Map key. Inspect the result in DevTools or the console and explain what you observed.
• 3Compare iterating a `Map` vs a plain object with `for...of`.