What are Nullish Coalescing and Optional Chaining?

interface User {
  name: string;
  address?: {
    city?: string;
    zip?: string;
  };
}

const user: User = { name: "John" };

// Without optional chaining
const city1 = user.address && user.address.city;

// With optional chaining
const city2 = user.address?.city; // undefined, no error

// Also works with methods and arrays
const length = user.name?.length;
const first = users?.[0];
const result = obj.method?.();

// ?? only triggers on null/undefined
const value1 = null ?? "default";    // "default"
const value2 = undefined ?? "default"; // "default"
const value3 = 0 ?? "default";       // 0
const value4 = "" ?? "default";      // ""
const value5 = false ?? "default";   // false

// Compare with ||
const value6 = 0 || "default";       // "default" (falsy!)

const city = user.address?.city ?? "Unknown City";
const port = config.server?.port ?? 3000;