Map (Key-Value Storage)

• new Map(iterable?) → Creates a Map object.
• .set(key, value) → Adds a key-value pair.
• .get(key) → Retrieves the value for a key.
• .has(key) → Checks if a key exists (true/false).
• .delete(key) → Removes a key.
• .clear() → Removes all entries.
• .size → Returns the number of key-value pairs.

const map = new Map();
map.set('key', 'value');
console.log(map.get('key')); // 'value'
console.log(map.has('key')); // true
map.delete('key');
console.log(map.has('key')); // false

Iterating Over a Map

• .keys() → Returns an iterator of keys.
• .values() → Returns an iterator of values.
• .entries() → Returns an iterator of [key, value] pairs.
• forEach(callback) → Iterates over key-value pairs.

const map = new Map([['a', 1], ['b', 2]]);
for (let [key, value] of map) {
  console.log(key, value); // 'a' 1, 'b' 2
}

Note: Map preserves key order unlike plain objects.

Set (Unique Values Collection)

• new Set(iterable?) → Creates a Set object.
• .add(value) → Adds a value.
• .has(value) → Checks if a value exists (true/false).