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TypeScript
React
Node.js
Next.js
AngularWhy TypeScript
TypeScript adds static types to JavaScript. Types describe the shape of data and functions, so editors can autocomplete accurately and the compiler can catch mistakes — a misspelt property, a missing argument, an unexpected null — before the code runs.
For growing codebases and teams, TypeScript is one of the most effective investments in quality. It makes refactoring safer, documents intent and helps new developers understand unfamiliar code quickly.
When TypeScript is the right choice
| Details | |
|---|---|
| Great fit | Any JavaScript project expected to grow or be maintained by several developers |
| Consider alternatives | Very small scripts or prototypes where type safety adds little value |
What we build with TypeScript
Full-stack TypeScript apps
Shared types between React front end and Node.js back end.
JavaScript → TypeScript migration
Gradual, file-by-file conversion with no big rewrite.
Type-safe APIs
Generated types from OpenAPI, GraphQL or tRPC.
Libraries & SDKs
Well-typed packages your team and partners can use.
Our TypeScript toolkit
Migrating from JavaScript
Migration does not need to stop feature work. We start by adding TypeScript to the build so JavaScript and TypeScript files coexist, convert shared utilities and types first, and then convert files as they are touched. Strictness settings are increased gradually. Within a few months, most of the codebase is typed and the team is shipping with more confidence.
Adopting TypeScript in an existing JavaScript codebase
You do not need to stop feature work to adopt TypeScript. Because TypeScript compiles plain JavaScript, a codebase can be converted gradually, and teams typically see value within the first few weeks.
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Add the compilerWeek 1
Introduce TypeScript with allowJs so existing files keep working, and add type checking to CI.
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Type the boundariesWeeks 1–3
Type API responses, shared models and utility modules first — where errors spread furthest.
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Convert by areaOngoing
Rename files to .ts as they are touched for features or fixes, rather than converting everything at once.
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Tighten settingsOngoing
Enable strict mode flags one at a time and reduce any-types until the codebase is fully strict.
Types that keep front end and back end in sync
Many production bugs happen at the boundary between services: the API changes and the client is not updated. TypeScript can close that gap. Options include generating types from an OpenAPI specification, using tRPC for end-to-end type safety between a TypeScript server and client, or sharing a schema library such as Zod that validates data at runtime and produces static types from the same definition. Runtime validation matters because TypeScript types disappear after compilation — data arriving from users, third-party APIs or databases still needs to be checked.
Where TypeScript is not enough on its own
Types prevent a large class of mistakes but do not replace tests, code review or good architecture. Overly clever generic types can also make code harder to read than the JavaScript they replaced. We favour simple, explicit types that document intent, and reserve advanced type features for shared libraries where they genuinely remove repetition.
TypeScript beyond the browser
TypeScript is now common across the whole stack. On the server it powers Node.js APIs built with NestJS, Fastify or Express, and newer runtimes such as Deno and Bun run TypeScript directly. Infrastructure can be written in TypeScript with the AWS CDK or Pulumi, and mobile apps with React Native. Using one language across front end, back end and infrastructure lets small teams move between layers easily and share validation logic and models. It is not always the right choice — Python remains stronger for data science and Go for some high-performance services — but for product teams building web applications, a TypeScript-first stack is a sensible, well-supported default.
Strictness settings that matter
| Compiler option | Why we enable it |
|---|---|
| strict | Turns on the core family of safety checks, including strict null checks |
| noUncheckedIndexedAccess | Forces handling of missing array items and dictionary keys |
| exactOptionalPropertyTypes | Distinguishes “missing” from “explicitly undefined” |
| noImplicitOverride | Makes inheritance changes explicit and safe |
| noFallthroughCasesInSwitch | Prevents a common class of logic bugs |
On a new project we enable these from day one. On an existing codebase we turn them on one at a time, fixing errors folder by folder so the build never stays red for long.
Validating data at the edges
TypeScript types disappear at runtime, so data from APIs, forms, environment variables and third-party webhooks must be validated before the rest of the code trusts it. We define schemas with libraries such as Zod or Valibot, infer the TypeScript types from those schemas and validate at every boundary. The result is one source of truth: if an external API changes shape, the error appears at the boundary with a clear message instead of as an obscure crash deep in the application.
Monorepos and shared types
When a web app, mobile app and back end are all written in TypeScript, a monorepo lets them share types, validation schemas and utilities.
- Workspace tooling such as pnpm workspaces with Turborepo or Nx
- A shared package for API contracts and schemas, versioned with the code that uses it
- Project references so each package type-checks independently and builds stay fast
- Clear boundaries so UI code never imports server-only modules
This removes a whole category of integration bugs where the front end and back end disagree about the shape of data.
A typical JavaScript-to-TypeScript migration
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Set up1 week
Add the compiler with allowJs, configure the build and CI, and agree conventions.
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Type the boundaries1–3 weeks
API clients, shared models and utility modules first — the code everything depends on.
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Convert by areaOngoing
Rename files as features are touched, adding types and tests together.
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Tighten2–4 weeks
Enable strict options progressively and remove remaining any types.
Durations are typical for a mid-sized application; feature work continues throughout.
Measuring the payoff
- Fewer production errors of the “undefined is not a function” kind, tracked in your error monitoring
- Faster, safer refactoring — the compiler lists every place a change affects
- Shorter onboarding because types document how modules fit together
- A shrinking count of any types and type-check suppressions, tracked in CI
TypeScript underpins our React, Next.js, Angular and Node.js work.
Common TypeScript anti-patterns
- Widespread use of
any, which silently switches type checking off - Type assertions (
as) used to silence errors instead of fixing the data flow - Duplicated interfaces for the same data in front end and back end
- Overly clever generic types that few people on the team can read or change
- Types that claim API data is safe without any runtime validation
We fix these gradually, with lint rules that stop new instances appearing while existing ones are cleaned up as code is touched.
TypeScript on the back end
TypeScript works just as well on servers as in browsers. With Node.js, Deno or Bun, frameworks such as NestJS, Fastify and Hono, and ORMs such as Prisma or Drizzle, a back end can share types with its clients and catch query mistakes at compile time. For teams already writing TypeScript in the browser, one language across the stack simplifies hiring and lets developers move between front end and back end work easily.
Work with us
Part of our frontend and Node.js work. See also React development.
This page is part of Frontend Development Services — see the full overview for related services, approach and pricing.