TypeScript

What TypeScript is

TypeScript is an open-source programming language developed by Microsoft and first released in 2012. It’s built directly on top of JavaScript, in fact it’s a superset of it, meaning any valid JavaScript is already valid TypeScript. What it adds is static types: a way to describe the shape of the data your code works with, so the editor and compiler can check that everything fits together before the code ever runs.

In plain terms, if a piece of code expects a customer’s name and email in a particular shape, TypeScript will flag it the moment something doesn’t match, a renamed field, a typo, a value of the wrong kind. These checks happen during development, on the developer’s screen, not in front of a visitor. When the project is built, TypeScript compiles down to ordinary JavaScript that runs in every browser, so there’s no runtime penalty for the extra safety.

How HDC uses TypeScript

TypeScript runs through our builds wherever code does real work. In practice that means:

• We write our site logic and React interactive islands in typed TypeScript, so mistakes surface during development rather than on a live page.
• We lean on Astro’s typed Content Collections, which use TypeScript to validate structured content, services, locations, blog posts, so a missing or malformed field is caught at build time, not after publishing.
• We use the types as a safety net when updating or refactoring a larger site: change one thing and the compiler immediately flags everything else that needs to change with it.
• We let Vite compile the TypeScript as part of the build with no extra setup, and keep it tidy with Prettier.

Why we apply it

For a client, the value of TypeScript is reliability. The bugs that hurt most on a business website are the quiet ones, a contact form that silently sends the wrong data, a broken link in a template that repeats across dozens of pages, a value that’s occasionally missing. These are exactly the mistakes TypeScript is built to catch, and it catches them on our screens during development rather than on a live page in front of a paying customer.

That matters twice over for businesses whose website is a lead source. A more robust site means fewer issues reaching visitors, and typed code is far safer to change later, so the new pages, seasonal updates and tweaks a site needs over the years can be made quickly and confidently, without fear of quietly breaking something elsewhere.

How TypeScript fits our stack

TypeScript is the language layer that makes the rest of our stack safer. It builds on JavaScript and compiles back down to it, so it runs anywhere. It underpins Astro’s typed Content Collections, giving structured content a validated shape; it’s the language our React islands are written in; it’s compiled seamlessly by Vite during the build; and it’s kept tidy by Prettier. Together those pieces mean the code behind a client’s site is not just fast, but dependable, and dependable code is what keeps a site working reliably long after launch.

When TypeScript isn’t the right tool

We’re honest about fit. For a tiny one-off script or the simplest static page, TypeScript’s extra structure can be more than the job warrants, and plain JavaScript is fine. It’s also important to be clear about what it does and doesn’t do: type checking happens during development, so data coming from a real user or an external system still needs validating at runtime, TypeScript reduces our mistakes, not a visitor’s bad input. For the real client sites we build, where reliability and easy long-term updates genuinely matter, those trade-offs are well worth it, which is why we reach for it by default.