TypeScript strict null checks — handling nullable types

After enabling strict or strictNullChecks, hundreds of TypeScript errors appear. Properties that were previously accessible now show 'Object is possibly null or undefined'.

This is correct — those were all potential runtime crashes. Fix strategies: (1) Optional chaining: obj?.prop?.nested. (2) Nullish coalescing: value ?? defaultValue. (3) Type guards: if (value !== null) { / value is narrowed / }. (4) Non-null assertion: value! — only when you are certain (avoid in most cases). (5) Define types accurately: use T | null explicitly. (6) Use required fields in interfaces, make optional fields explicit with ?. (7) For gradual migration: enable strictNullChecks and fix file-by-file using // @ts-expect-error temporarily.

Without strictNullChecks, TypeScript assumes every type includes null and undefined implicitly. Enabling it makes the type system accurately model nullable values, catching real bugs.