TypeScript Development Services

A full-codebase rewrite to TypeScript is rarely the right move; TypeScript supports incremental adoption because it can type-check a mix of .ts and .js files in the same project. We typically start by enabling `allowJs` and `checkJs`, adding types to the modules with the most bugs or the most churn first, and letting the rest of the codebase convert opportunistically as files are touched for other reasons.

The modules worth converting first are usually the ones defining shared data shapes: API clients, core domain models, utility functions used everywhere. Converting those early gives the rest of the migration a typed foundation to build on, rather than typing UI components first and hitting untyped data flowing in from everywhere.

Type safety at compile time does not replace runtime validation at the edges of a system. Data from an external API, user input, or a third-party webhook has a shape the compiler cannot verify, because the compiler only checks the code you wrote, not the data arriving from outside it. A common failure mode is a team trusting a TypeScript interface for a shape that was never actually validated at runtime, and getting a production crash when the external service sends something slightly different than expected.

We pair static types with Zod schemas at every external boundary specifically to close that gap: the schema validates the data is what it claims to be, and infers the TypeScript type from the same definition, so there is one source of truth instead of two that can drift apart.