- TypeScript – Interview Questions
The questions a TypeScript role actually asks, answered against the twenty lessons before this one. any versus unknown, interface versus type, why enum is contentious, what structural typing means in practice, how narrowing works, what erases at build time and what does not. Short answers, with the reasoning behind them.
- NestJS – Interview Questions
The questions that actually get asked, with answers drawn from the nineteen lessons before this one — module scope and why a provider is not global, guards versus middleware versus interceptors, how Nest resolves a dependency, why the global ValidationPipe matters, and what happens to an exception on its way out.
- iOS – Taking Payments with Stripe
PaymentSheet rather than a card form of your own, and the PCI reason that is not negotiable. The two-step order-then-pay flow and why it has to be two steps, quarantining the SDK behind a protocol so checkout is testable, bridging a completion handler into async, and the dismissed sheet that is not an error.
- TypeScript – With React
Typing props and children, useState where inference is enough and where it is not, useRef's two different types, event handlers, and generic components. Plus the context pattern that removes the `| undefined` every consumer would otherwise have to handle, taken from this app's auth provider.
- NestJS – Testing
Test.createTestingModule, mocking a provider with useValue, and getting the token right — @InjectDataSource does not ask for the class, so overriding the class leaves your test talking to the real database. Then e2e with supertest, and the trap that makes a whole suite pass vacuously: forgetting the global pipe.