Web App Development
TypeScript Web App Development in Strict Mode, End to End
We build TypeScript web apps with strict mode enforced, Zod schemas for runtime validation, and type-safe API contracts — so the compiler catches bugs before your users do.
TypeScript Web App Development Done Right, Not Just in Name
TypeScript is not just a linter — it is a communication layer between every part of your codebase. When your API returns a User object with 40 fields, TypeScript ensures every component that accesses that User knows which fields exist, which are optional, and which might be null. That type safety eliminates an entire category of runtime errors that would otherwise surface in production, usually during a demo or at peak traffic. We have never shipped a TypeScript web app that failed at runtime because of a missing property — because the compiler caught it first.
The difference between TypeScript 'with types' and TypeScript 'done correctly' is enormous. Projects that scatter any throughout the codebase, disable strict mode in tsconfig, or skip typing async function return values get 20% of the safety with 100% of the configuration overhead. We run TypeScript in strict mode with noImplicitAny, strictNullChecks, and exactOptionalPropertyTypes enforced — and we maintain zero any-type suppressions. This feels slower in week one and dramatically faster from week three onward as the compiler prevents an entire class of bugs.
TypeScript web app development at its best means building the API contract between frontend and backend into the type system itself. We use Zod schemas to validate API responses at runtime and derive TypeScript types from those schemas, ensuring your database schema, API layer, and UI components agree on data shapes as the codebase evolves. Schema drift — where the database has a column your frontend does not know about, or vice versa — is one of the most common sources of production bugs. TypeScript with Zod makes it structurally impossible.
Our Approach to Typescript web app development
Every project follows our 4-step vibe-coding process — AI handles the boilerplate, senior engineers handle the craft. From idea to live product in 3–7 days for MVPs.
Discovery
We audit the type requirements of your data model before writing any code: which entities exist, how they relate, which fields are required versus optional, and which types vary by user role or subscription tier. These decisions become the TypeScript type definitions that anchor the entire codebase — getting them right upfront prevents expensive refactoring when business requirements evolve.
Design
We design the shared type library — the TypeScript interfaces for your domain entities — before designing the UI or API. Database schema, API response types, and component prop types all derive from the same core entity definitions. This single-source-of-truth approach means changing a type in one place propagates through the entire codebase with TypeScript showing you every affected location.
Build
TypeScript strict mode throughout, Zod for runtime validation of all external data (API responses, form inputs, environment variables, URL parameters), shared type packages between frontend and backend, TypeScript generics for reusable utility functions and data fetching hooks. AI generates the boilerplate TypeScript scaffolding; our engineers write every type definition and Zod schema by hand.
Launch
TypeScript build check in CI: zero type errors required before merge. We run tsc --noEmit in the CI pipeline, making TypeScript errors a hard merge blocker. We also run the TypeScript compiler in watch mode during development so type errors surface at the moment they are introduced, not at code review or build time.
What You Get
Every typescript web app development engagement includes these deliverables — scoped before we start, delivered before we invoice.
- TypeScript strict mode configured with noImplicitAny, strictNullChecks, and exactOptionalPropertyTypes
- Shared domain type library: all entity interfaces and union types in one source of truth
- Zod schemas for runtime validation of API responses, form inputs, and environment variables
- TypeScript generics for reusable data fetching hooks and utility functions
- Type-safe API route handlers with request and response types enforced at compile time
- Database type generation from Supabase schema for end-to-end type safety
- CI pipeline: tsc --noEmit as a required passing check before every merge
- TypeScript path aliases configured so imports use @/components instead of relative paths
- Type-safe environment variable access using a validated env module
- Zero any-type suppressions: ESLint rule @typescript-eslint/no-explicit-any set to error
Tech Stack We Use
TypeScript web app development at Greta uses TypeScript 5 in strict mode with every safety flag enabled. We generate database types directly from the Supabase schema using the Supabase CLI, so your TypeScript types and your database columns never drift apart. API response types are defined with Zod schemas that validate at runtime and derive TypeScript types statically — one definition that serves both purposes. Environment variables are validated at startup with a Zod schema, making a missing environment variable a startup failure rather than a runtime crash hours later. We use TypeScript path aliases for clean imports and configure the TypeScript project references for monorepo setups where frontend and backend share types. The result is a codebase where the compiler enforces correctness at every layer.
Case Study
PLGOS — TypeScript End-to-End Across a Complex SaaS
PLGOS has a complex data model: organizations, users, integration events, A/B test definitions, activation criteria, and real-time subscription states. Without TypeScript strict mode, maintaining the invariants between these entities would require extensive runtime checks and defensive programming throughout. We built PLGOS with TypeScript strict mode, Supabase-generated database types, and Zod schemas for all API boundaries. The TypeScript compiler caught 23 type errors during development that would have been production runtime bugs — including a null reference on the activation event object that would have caused the dashboard to crash for users whose first event arrived during an edge-case timing window.
Read full case studyPricing Transparency
TypeScript web app development does not carry a premium over standard development — it is our default for every project. The speed benefit of catching type errors at compile time more than offsets any overhead from writing type annotations. All projects include TypeScript strict mode, Zod validation, and CI pipeline type checking. Pricing starts at $5,000 for MVPs and $15,000+ for full builds.
MVP
From $5,000
3–7 business days
Full Build
From $15,000
2–4 weeks
All projects include full code ownership, two revision rounds, Vercel deployment, and one week of post-launch support. No hidden fees.
Frequently Asked Questions
Do you use TypeScript by default or only when requested?
TypeScript strict mode is our default on every project. We do not start new projects in JavaScript. The type safety benefit — catching property access errors, nullable value bugs, and API contract violations at compile time — is too significant to skip for a modest configuration overhead.
What does TypeScript strict mode include?
Strict mode enables several compiler flags: noImplicitAny (you cannot use untyped variables), strictNullChecks (undefined and null are not valid substitutes for typed values), strictFunctionTypes (function parameter contravariance), and several others. Together, they eliminate the most common categories of TypeScript runtime bugs that occur with non-strict configuration.
How do you validate API responses at runtime?
We use Zod schemas to validate API responses at the boundary where external data enters the application — fetch calls, webhook payloads, URL parameters. Zod parses and validates the data structure, throwing a typed error if the response does not match the expected schema. This catches API contract violations — like a field name change on the backend — immediately rather than hours later when undefined causes a crash.
Can you add TypeScript to an existing JavaScript project?
Yes. We migrate JavaScript projects to TypeScript incrementally: start with allowJs: true so TypeScript files coexist with JavaScript, add types to the most critical files first, and progressively enable stricter compiler flags as more files are typed. A full migration to strict TypeScript on a large JavaScript project typically takes 1–3 weeks depending on codebase size.
How do you keep database types and TypeScript types in sync?
We generate TypeScript types directly from the Supabase database schema using the Supabase CLI generate types command. This runs in CI whenever the database schema changes, producing a types file that reflects the current schema. If a database column is renamed, the generated types change and TypeScript shows every affected usage — making schema drift a compile-time error rather than a runtime surprise.
What is the performance overhead of TypeScript?
Zero at runtime — TypeScript compiles to plain JavaScript and all type annotations are erased. The overhead is at compile time: tsc adds seconds to your build. We configure incremental compilation and TypeScript project references to keep compile times manageable as the codebase grows. In development, Turbopack handles TypeScript transpilation without full type checking for fast hot reloads.
Do you use TypeScript decorators or class-based patterns?
We avoid decorators and class-based TypeScript patterns in new projects. They add complexity without benefit for functional React and Next.js codebases. We use plain interfaces, type aliases, and generic functions — the patterns that are idiomatic in modern TypeScript and compatible with React Server Components.
How do you type environment variables?
We create an env.ts module that reads from process.env, validates every required variable with Zod, and exports typed constants. Any code that needs an environment variable imports from env.ts instead of process.env directly. If a required variable is missing at startup, the Zod validation throws a clear error naming the missing variable rather than crashing cryptically later.
Ready to ship?
Ready to build your TypeScript web app?
Start Your ProjectOr reach us directly at hello@greta.agency
Written by the Greta Agency team · Last updated April 2025