Language
TypeScript development
TypeScript adds a description of the data to JavaScript, and checks the code against it before anything runs. We write most new web and server code in it, and we move older JavaScript across in stages.
- 1,200+ clients helped
- Building since 2010
- 15 services, one team
- 50+ technologies
At a glance
What it is
TypeScript is JavaScript with a description of what each piece of data looks like, so many mistakes are caught while the code is written instead of after release.
Problems it solves
JavaScript projects grow until nobody is sure what a function expects, and small mistakes reach customers.
Who it suits
Teams starting a web or server project, and owners of a JavaScript codebase that has become risky to change.
How to choose
Use TypeScript for anything that will be changed by several people over several years. Skip it only for small, short-lived scripts.
What it means
JavaScript that knows what it is handling
TypeScript is JavaScript with types: a written description of what each value is. A checker reads those descriptions and reports where the code does not match, before it ever runs.
That matters most where several people change the same code over time. The descriptions act as documentation that cannot go out of date, because the checker would complain.
It compiles to ordinary JavaScript, so it runs anywhere JavaScript does: in browsers, on servers, and in tools. Nothing about your hosting has to change.
Adopting it
Moving an existing project across
Turn on the checker gently
We add TypeScript to the project in a permissive mode, so existing files keep working while new files are checked.
What it produces
- Configuration
- First typed files
Type the edges first
We describe the data that enters and leaves the system, such as responses from an API (a way for programs to exchange data) and form input, because that is where mistakes begin.
What it produces
- Shared data types
Convert by importance
We move the files that change most, or hurt most when they break, and leave stable code alone.
What it produces
- Converted modules
- Fewer runtime errors
Tighten the rules
As coverage grows, we turn on stricter checking, one rule at a time.
What it produces
- Stricter configuration
What DECHY can do
Working with TypeScript
New projects
- Web applications and portals written in TypeScript from the first day.
- Server code that shares data descriptions with the interface.
Existing projects
- A staged move from JavaScript.
- Reviews that show where the riskiest untyped code is.
Team practice
- Conventions that keep types useful, not decorative.
- Handover notes and developer guidance.
Options
TypeScript compared with other choices
Suits
Web interfaces and server code that several people maintain.
- Trade-off
- A setup step, and some learning for developers new to types.
Plain JavaScript
Suits
Small scripts and short-lived prototypes.
- Trade-off
- Fewer safety nets as the code grows.
Suits
Data work, automation, and AI-related code.
- Trade-off
- Different language from the browser, so two skill sets.
Suits
Large back-end systems in organizations already using it.
- Trade-off
- More ceremony for small projects.
Typical uses
Where TypeScript pays for itself
A web application that several people change
Shared descriptions of the data keep one person's change from breaking another's screen.
A back end that serves a web and a mobile app
One set of data descriptions shared by every client, so the app and the site agree.
Integrations with outside services
Careful handling of data from payment, shipping, and customer-record systems, where surprises are expensive.
A long-lived codebase
Code that will be maintained for years by people who did not write it.
Common questions
Questions about TypeScript
Does TypeScript make the site faster?
No. It is removed before the code runs. The benefit is fewer mistakes and easier changes, not speed.
Will it slow development down?
A little at the start, and noticeably less later. Changes to shared code become safer, which is where time is usually lost.
Can we mix TypeScript and JavaScript?
Yes. That is how most migrations work, and it lets the move happen alongside normal feature work.
Is it only for front-end code?
No. It is used just as often on servers, including with frameworks such as Next.js.
Have a different question?
Tell us what you are weighing up and we will answer it plainly.
Ask a questionAlready a client? Email support@dechytech.com
Technical depth
How we build with TypeScript
What we settle early on TypeScript work: strictness, types at the boundary, and avoiding false confidence, so nothing surprises your team later.
We aim for strict mode on new code. The checker finds more problems, and the cost of turning it on later is higher than starting with it.
- Runtime validation of external data, since types disappear after compilation and cannot protect against a bad response.
- Generated types from API descriptions where the provider offers them.
- Strictness introduced gradually, starting with the files that change most, so delivery does not stop and reviews stay small.
- Few uses of the any type, and none without a comment saying why.
- Code review that treats a forced type conversion as a flag.
Tell us about the codebase
Describe the project, how many people change it, and what breaks most. We will say whether to start in TypeScript or move there in stages.