TypeScript: режим `strict` и флаги — пример кода

// tsconfig.json — the baseline every new project should ship
{
  "compilerOptions": {
    "strict": true,
    // Not in `strict`, but you almost always want them:
    "noUncheckedIndexedAccess": true, // arr[i] is T | undefined — forces bounds handling
    "noImplicitOverride": true,       // must write `override` when overriding
    "noFallthroughCasesInSwitch": true
  }
}

// strictNullChecks OFF → this compiles and crashes at runtime:
function greet(name: string) { return name.toUpperCase(); }
greet(null as any);  // ❌ no error without the flag; 💥 TypeError at runtime

// strictNullChecks ON → the compiler forces the guard:
function greetSafe(name: string | null) {
  if (name == null) return "hi";        // ✅ must narrow first
  return name.toUpperCase();
}

// noUncheckedIndexedAccess ON → the off-by-one the type system now catches:
const xs = [1, 2, 3];
const first = xs[0];   // type is number | undefined, not number
first?.toFixed();       // ✅ handle undefined