feat: add modern js

Author: ExploitEngineer

part9 (Advanced Topics)/Modern_JavaScript/modern_JS.js

@@ -0,0 +1,66 @@
+// INFO: ES6 Primitives & Meta Types 
+
+/*
+1. Symbols
+Unique and immutable values, ideal for object keys that shouldn't collide.
+*/
+const id = Symbol("userID");
+obj[id] = 123;
+
+/*
+2. BigInt
+For integer values beyond Number.MAX_SAFE_INTEGER
+*/
+const big = 9007199254740991n + 1n;
+console.log(big); // 9007199254740992n
+
+/*
+3. Sets
+Stores unique values.
+Good for deduplication
+*/
+const s = new Set([1, 2, 2, 4]);
+console.log([...s]);
+
+/*
+4. Map
+key-value store with any type as key (including objects)
+*/
+const m = new Map();
+m.set({ id: 1 }, 'data');
+
+/*
+5. Proxy & Reflect
+proxy lets you intercept operations like get/set
+*/
+const p = new Proxy({}, {
+  get: (obj, prop) => prop in obj ? obj[prop] : 42
+});
+console.log(p.any); // 42
+
+/*
+6. Destructuring
+Simplifies extracting values
+*/
+const { a, b } = obj;
+const [x, y] = arr;
+
+/*
+7. Optional Chaning(?.)
+Safely access nested properties or methods
+*/
+const user = {
+  name: "Alice",
+  address: {
+    city: "New York",
+    zip: 10001
+  }
+};
+console.log(user.address?.city); // "New York"
+console.log(user.contact?.phone); // undefined (no error)
+
+/*
+8. Nullish (??)
+Default only if value is null or undefined
+*/
+const n = val ?? "defalut";