feat: add keyed collections in js

Author: ExploitEngineer

part9 (Advanced Topics)/Data Structures/keyed-collections.js

@@ -0,0 +1,69 @@
+/*
+INFO: Keyed Collection in JavaScript
+Keyed Collection are special objects for storing collections of data using keys (like a map or a set).
+There are 4 types:
+*/
+
+/*
+INFO: 1. Map
+Stores key-value pairs.
+Keys can be any type (object, string, number, etc.)
+Maintains insertion order
+*/
+let collection = new Map();
+
+collection.set("key", 100);
+collection.set(window, 200);
+collection.set(5, 300);
+
+console.log(collection.get(window));
+console.log(collection.size);
+collection.delete(window);
+console.log(collection.size);
+collection.clear();
+console.log(collection.size);
+console.log(collection.keys());
+console.log(collection.values());
+
+let coll = new Map([
+  ["key", 100],
+  [window, 200],
+  [5, 3],
+]);
+console.log(coll.get("key"));
+console.log(coll.get(window));
+console.log(coll.get(5));
+
+/*
+INFO: 2. WeakMap
+Like Map, but:
+Only objects as keys
+Keys are weakly referenced (don't prevent garbage collection)
+Not iterable (you can't loop through it)
+*/
+let obj = {};
+let weakMap = new WeakMap();
+weakMap.set(obj, "data");
+
+/*
+INFO: 3. Set
+A collection of unique values
+Can store any type of value
+No duplicate elements
+*/
+let set = new Set();
+set.add(1);
+set.add(2);
+set.add(1); // Duplicate, ignored
+console.log(set); // Set(2) {1, 2}
+
+/*
+INFO: WeakSet
+Let Set, but:
+Only stores objects
+Objects are weakly held
+Not iterable
+*/
+let object = {};
+let weakSet = new WeakSet();
+weakSet.add(obj);