Technology Expertise
TypeScript Development & AI Integration
We build web applications and APIs in TypeScript, set up to suit the codebase and what the client asks for, so the database, the API and the interface can describe the same data the same way. We also convert existing JavaScript codebases to TypeScript, one module at a time, without stopping the product.
Start a TypeScript project →What TypeScript expertise does Code and Trust have?
Code and Trust builds in TypeScript across the stack when a project calls for it: types derived from the database schema, data validated where it enters the system, and types carried through to the components. How strict the setup is depends on the codebase and the scope. The point is a codebase a new engineer can change with confidence. We also migrate JavaScript applications to TypeScript incrementally, while the product keeps shipping.
Setting up TypeScript for a project
How strict a TypeScript setup should be depends on the codebase, the team and what the client asks for, so we decide it per engagement. On a new project, strict mode from the first commit is usually the cheaper choice, because turning it on later means fixing hundreds of errors at once, and teams rarely do. TypeScript's strict flag switches on a family of checks that the language's own documentation describes as giving "stronger guarantees of program correctness" (TSConfig reference: strict, read 2026-09-30). The options below are the ones we weigh; none of them is a fixed stack.
- →Strict compiler settings, including
noImplicitAnyandstrictNullChecks - →Lint rules that flag
anyand unchecked type assertions in review - →Type checking in continuous integration, so a type error blocks a merge
- →Type-safe database access through an ORM or query builder, such as Drizzle or Prisma, where the project has a database layer to type
One definition of the data, from database to screen
Many production bugs in web applications are disagreements about data: the API sends a field the interface does not expect, or a column becomes nullable and nobody tells the frontend. Where the scope allows, we define each shape once and derive the rest from it. Database types come from the schema, request and response types come from shared schema definitions or an OpenAPI description, and components receive those types rather than a hand-copied version. When a shape changes, the compiler lists every place that has to change with it.
What types do not catch, and what we do about it
TypeScript checks your code, not your data. Type annotations are removed when the code is compiled, and they "never change the runtime behavior of your program" (TypeScript handbook, The Basics, read 2026-09-30). So a malformed request, a changed third-party API or an unexpected database value can still arrive with the wrong shape. The answer is to validate data where it enters the system, for example with a schema library such as Zod, so the types inside the application describe data that has actually been checked.
- →Validation of request bodies, query strings and webhook payloads at the API boundary
- →Validation of responses from third-party APIs and language models before they are used
- →Parsing of environment variables at startup, so a missing setting fails loudly on deploy
- →Tests for behaviour, because correct types do not mean correct logic
Migrating a JavaScript codebase to TypeScript
A JavaScript application does not have to be rewritten to get the benefit. The TypeScript compiler can check a project that mixes JavaScript and TypeScript files, with the allowJs option documented for exactly this (Migrating from JavaScript, read 2026-09-30). A conversion goes module by module, starting with the shared code that everything else depends on, releasing as we go, and tightening the compiler settings as each area is finished; the exact plan depends on the codebase. The product keeps shipping throughout; nothing waits for a big-bang conversion.
- →An inventory of the codebase and its riskiest shared modules before anything changes
- →Types added to shared data shapes and API boundaries first, where they catch the most
- →Compiler strictness raised area by area, with the remaining gaps tracked, not hidden
- →Existing tests kept green at every step, and new tests where coverage is thin
Why Code and Trust uses TypeScript
Code and Trust selects TypeScript for projects where it provides a demonstrable engineering advantage: better performance, lower operational overhead, or faster iteration cycles. Every technology choice is justified by requirements, not familiarity.
Production-proven
Our TypeScript implementations run in production at enterprise scale, not greenfield experiments. We understand the failure modes.
AI-native integration
We combine TypeScript with modern LLM APIs and AI tooling, not as an add-on, but as a core architectural decision from day one.
Handoff-ready
Every project ships with inline documentation, automated tests, and a knowledge transfer session, so your team can own and extend it independently.
TypeScript projects: common questions
Do you always use TypeScript?
No. It depends on the client, the codebase and what the project needs, and we work in plenty of other languages. For web applications and APIs TypeScript is a common choice, and how strictly it is configured is decided per engagement. For a small one-off script, plain JavaScript or Python is often the better fit.
Does TypeScript prevent runtime errors?
It prevents a large class of mistakes in your own code, but it does not check data at runtime: types are removed when the code is compiled. That is why requests, webhooks and third-party responses should be validated at the boundary, so the types inside the application describe data that has been checked.
Can you convert our JavaScript app to TypeScript without a rewrite?
Yes. The compiler can check a mixed JavaScript and TypeScript codebase, so we convert module by module, shared code first, releasing as we go. The product keeps shipping, and strictness is raised as each area is finished.
How long does a JavaScript to TypeScript migration take?
It depends on the size of the codebase and how much of it is tested, so we scope it after reading the code rather than quoting blind.
What does a TypeScript project cost?
Most large builds are fixed-price, with a monthly retainer after launch. Builds start from $15,000, scoped after the 90-minute AI workflow audit, which is complimentary when it is bundled with a larger build and available as a paid one-off on its own. Most new builds run 8–16 weeks from kickoff to production.
Start a TypeScript project with Code and Trust
Tell us what you're building. We'll scope it, resource it, and give you a fixed-price quote, with no billing-by-the-hour surprises.
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