TypeScript development for JavaScript projects that need to stay reliable
- Type checking before code reaches users
- Gradual migration, file by file
- Shared types between front end and back end
- Honest limits: types do not check data at runtime
When TypeScript is the right choice
TypeScript helps most where code is large, shared or long-lived:
- A JavaScript codebase that several people change and that breaks in surprising places after small edits.
- A front end and a back end that exchange data and drift apart. Shared type definitions make a mismatch a build error instead of a production bug.
- A project built on frameworks that are designed around it, such as NestJS and Angular, or one using React or Vue with TypeScript.
- A codebase you expect to hand to new developers, who read types as documentation.
When TypeScript is not the right choice
TypeScript has a cost in setup and learning, and some projects do not repay it:
- A few lines of script on a marketing page. Plain JavaScript is enough.
- A short-lived prototype that will be thrown away.
- A team under heavy deadline with no one who knows TypeScript. Introduce it at a quieter time, starting with the loosest settings.
- A belief that it replaces testing or input checks. It does not; see below.
What we do with TypeScript
New projects
Strict settings from day one on front ends and back ends, with shared types for the data that crosses between them.Migrating JavaScript
Adding TypeScript to an existing project in steps, so the code keeps shipping while coverage grows.Tightening existing TypeScript
Replacing loosely typed code with real types, and adding runtime validation where outside data enters.Reporting
Pull the numbers from several systems on a schedule, write the summary, and point out what changed and why it might matter.Back-office reconciliation
Match payments, orders and invoices across systems and prepare the mismatches for review.Your workflow
If a task is repetitive, rule-heavy and checked by someone anyway, it is a candidate. The AI readiness audit ranks the candidates.What types protect, and what they do not
TypeScript removes its types when it compiles. A value you declared as a string is not checked again while the program runs, so data arriving from a form, an API or a database can still be the wrong shape. The type system tells you the truth about your own code; it cannot vouch for the outside world. We add runtime validation at every boundary, such as request bodies and third-party responses, and write tests for the logic that matters. Types plus validation plus tests is the combination that reduces bugs; types alone do not.
Moving a JavaScript project over
You do not have to convert everything at once. TypeScript can be configured to allow JavaScript and TypeScript files side by side, so a project can be migrated gradually. A common order is: add the compiler with permissive settings, type the shared data models, convert the files that change most, then turn on stricter checks as the warnings reach zero. Each step ships on its own. If the migration is part of a wider rebuild, see website modernisation, and for the Node.js side our Node.js page.
How we work
- Scope first: we agree what the first release must do, what can wait, and what it depends on, in writing.
- Build in increments: you see working software on a staging site regularly, not one large hand-over at the end.
- Test as we build: automated tests for the logic that matters, and a manual check of the journeys your customers use.
- Hand over properly: the code in your repository, documentation, and a walkthrough so your team or ours can carry on.
What we have built
We have built many websites with TypeScript. We describe our work in general terms here and do not publish client names or figures; ask us on a call what is relevant to your project.
Frequently asked questions
Is TypeScript a different language from JavaScript?
TypeScript is JavaScript with a type system added. It compiles to plain JavaScript, so browsers and Node.js run the result without needing anything extra.
Will TypeScript slow our team down?
There is a learning period and some extra typing. Teams usually recover that when changes become safer and editors can suggest and check code. We introduce it gradually and agree the strictness level with your team.
Can we adopt TypeScript without rewriting everything?
Yes. JavaScript and TypeScript files can live in the same project, so you can migrate file by file.
Does TypeScript make an application secure or bug-free?
No. It catches a certain kind of mistake, using a value where another kind was expected, before the code runs. It does not validate data at runtime, replace tests, or fix logic errors.
Sources
Technology facts on this page are taken from the official documentation:
Is your JavaScript getting hard to change?
Tell us about the codebase and who works on it. We will say whether TypeScript will pay off, and where to start.
