TypeScript development company
We write TypeScript for browser, server and edge code, and we convert untyped JavaScript codebases file by file, tightening compiler settings as coverage grows so types catch real bugs instead of decorating them.
- Senior engineers · IST + EST overlap
- NDA on day 1
- 24-hour reply
- Projects shipped
- 50+
- Code ownership
- 100%
- Client rating
- 4.8/5
- First reply
- 24h
TypeScript that the compiler can actually enforce
When a JavaScript codebase grows past the point where tests and review alone keep it safe to change, Krapton steps in as a TypeScript development company. TypeScript adds a static type system on top of JavaScript, and its value depends almost entirely on configuration and discipline: a codebase full of any, loose tsconfig settings and unchecked API responses gets the build step without the safety. Our engineers start new projects with strict mode, noUncheckedIndexedAccess and typescript-eslint rules that flag unsafe any usage, then validate every boundary where data enters the program, using Zod or Valibot schemas for HTTP bodies, environment variables and queue messages. For existing JavaScript, migration runs in stages with allowJs and checkJs, so modules convert one at a time while the application keeps shipping. You receive typed source, shared type packages in a pnpm or npm workspace, a CI step that runs tsc --noEmit on every pull request, and guidance your developers can follow when the next feature lands.
TypeScript development services
JavaScript to TypeScript migration
Staged conversion with allowJs, JSDoc types as a stepping stone, codemods for bulk renames, and a ratchet in CI that blocks new any usage while old modules are still converting.
Strict mode hardening
Turning on strict, noUncheckedIndexedAccess and exactOptionalPropertyTypes in existing projects, fixing the errors in priority order, and replacing casts with type guards and discriminated unions.
End-to-end typed APIs
Shared contracts between client and server through tRPC, OpenAPI-generated clients or GraphQL Code Generator, so a renamed field breaks the build instead of a production screen.
TypeScript backend services
NestJS, Fastify or Hono services with typed database access through Prisma, Drizzle or Kysely, and runtime validation at every request and webhook boundary.
Typed front ends
React, Next.js, Angular or Vue applications with typed props, typed routing and form schemas that share validation rules with the server instead of duplicating them by hand.
Monorepos and type libraries
Turborepo or Nx workspaces with project references, published declaration files, and internal packages versioned with Changesets so several apps can depend on one source of truth.
Why teams choose Krapton for TypeScript
Senior engineers, fixed scope, and code you own — the things agencies promise and rarely deliver.
Types checked at runtime too
TypeScript types vanish after compilation, so untrusted input is parsed with schema validators. That closes the gap where a third-party API changes shape and the compiler cannot know.
Readable types, not puzzles
Advanced generics and conditional types are used where they remove real duplication, not to show off. Types stay legible enough that a new hire can follow an error message.
Declaration files done properly
Untyped packages get local declaration files or DefinitelyTyped contributions instead of blanket any shims, and module resolution settings match how your bundler or Node.js actually loads code.
Migration without a freeze
Converted and unconverted files coexist during migration, so product work continues. Each pull request leaves the codebase slightly stricter than before rather than waiting for a single cutover.
How a TypeScript project runs with Krapton
01
Type health baseline
We measure any usage, suppressed errors, compiler flags and untyped dependencies, producing a ranked list of modules where stronger types would prevent the most bugs.
02
Contracts and boundaries
API schemas, shared domain types and validation rules are defined before features, giving front-end and back-end developers one agreed vocabulary to build against.
03
Iterative delivery
Features ship behind tests in Vitest or Jest and Playwright, with type checks, lint and unit tests required on every pull request.
04
Upgrade path documented
We record compiler settings, lint rules and remaining migration debt, plus how to upgrade TypeScript itself when a new release changes inference or deprecates options.
The TypeScript stack we build with
TypeScript development: questions answered
Why hire a TypeScript development company instead of adding types ourselves?
You can add types yourselves, and many teams should; outside help pays off when the migration keeps stalling or the types are not catching bugs. A TypeScript development company brings a tested migration order, compiler and lint settings that hold the line, and practice typing awkward areas such as legacy Redux, dynamic forms and third-party SDKs without falling back on any. The deliverable includes conventions your team keeps using afterwards.
Is TypeScript worth it for a small project or prototype?
Usually yes, though the case is weaker for throwaway scripts. Modern tooling such as Vite, Next.js and Bun handles TypeScript with almost no setup, and editor autocompletion pays back quickly even on small codebases. Where it can slow you down is heavy generic code in early prototypes; keep types simple until the domain settles. For a one-off data script or a tiny static site, plain JavaScript with JSDoc comments is a reasonable choice.
How do you migrate a large JavaScript codebase to TypeScript safely?
By converting in dependency order while the app keeps shipping. We enable allowJs, add a tsconfig that starts permissive, and convert leaf utilities and shared models first because everything else imports them. Pull requests stay small, renames are separated from logic changes, and a CI ratchet stops the count of any or ts-expect-error comments from rising. Strict flags are then enabled per package or folder-level tsconfig once each area compiles cleanly.
Does TypeScript slow down builds or runtime performance?
It adds essentially no runtime cost, because types are erased before code runs; build time is the real consideration. On large repositories, slow feedback usually comes from running full type checks inside the bundler. Separating transpilation, handled by esbuild, SWC or Vite, from tsc type checking, and using incremental builds or project references, keeps editor and CI times manageable. Overly clever recursive types can also slow the compiler and are worth simplifying.
What affects the cost of TypeScript development work?
Codebase size and current type health matter most. Typing an untested front end full of dynamic objects and implicit globals takes far more care than converting a well-tested Node.js service. The estimate also reflects how many external APIs need modeling, whether shared contracts span several apps, the strictness you want to end with, and whether migration runs alongside feature delivery or as a dedicated stream.
Ready to build? Tell us what you have in mind.
Send a short brief and a senior engineer will reply within one business day with next steps — no sales fluff.