Shipping fast without breaking TypeScript

Strict TypeScript and fast iteration aren't opposites — but you have to set the project up so the compiler works for you.

Turn on the strict flags early

{
  "compilerOptions": {
    "strict": true,
    "noUncheckedIndexedAccess": true
  }
}

noUncheckedIndexedAccess catches an entire class of undefined bugs that strict mode alone misses.

Infer, don't annotate

Let inference do the work. Annotate boundaries (function signatures, exported APIs) and let everything inside flow.

Model state with unions

Discriminated unions make impossible states unrepresentable:

type Result<T> =
  | { status: "loading" }
  | { status: "error"; error: Error }
  | { status: "success"; data: T };

The compiler then forces you to handle every case at the call site.