5. Operators and control flow

Beyond the arithmetic/comparison basics, three operators pull real weight in modern code:

const user = null;
user?.profile?.name;        // optional chaining: undefined instead of throwing
const name = user?.name ?? "Anonymous";  // nullish coalescing: only falls back on null/undefined

// vs the older, buggier `||` fallback:
const count = 0;
count || 10;   // 10 — WRONG if 0 is a valid value, `||` treats it as falsy
count ?? 10;   // 0  — CORRECT, ?? only falls back on null/undefined

switch uses === semantics and needs explicit break (fallthrough is intentional and common for grouping cases); prefer object-literal lookup tables or a Map over long if/else if chains for pure value dispatch.