TypeScript | What It Is & How I Use It

TypeScript is a superset of JavaScript that adds static type checking to the language. Developed and maintained by Microsoft, it compiles down to plain JavaScript and can run anywhere JavaScript runs, browsers, Node.js, Deno, Bun, or any other runtime. For custom web application development, TypeScript is non-negotiable in my stack. It catches entire categories of bugs at compile time that would otherwise only surface in production: null reference errors, missing properties, incorrect function arguments, and shape mismatches between API responses and frontend components. The type system is remarkably expressive, supporting generics, discriminated unions, mapped types, and conditional types. When paired with tools like Prisma or tRPC, TypeScript enables end-to-end type safety from the database schema through the API layer to the React component, meaning a column rename in the database immediately surfaces as a compile error everywhere it matters.

The Backstory

TypeScript was created by Anders Hejlsberg at Microsoft and publicly announced in October 2012. Hejlsberg was already a legendary language designer, he had created Turbo Pascal, led the development of Delphi, and was the chief architect of C#. The project began internally at Microsoft around 2010 when large teams working on products like Bing Maps and Office 365 found that JavaScript simply could not scale to codebases with hundreds of thousands of lines. Google had attempted to solve the same problem with Dart, which proposed replacing JavaScript entirely. Hejlsberg took a different approach: make a language that was a strict superset of JavaScript, so any valid JavaScript was automatically valid TypeScript, and the types could be adopted incrementally.

Under the Hood

TypeScript's compiler is itself written in TypeScript, a property called self-hosting or bootstrapping. This means the TypeScript team dogfoods their own language in the most extreme way possible: every bug in the type checker is also a bug in the tool they use to build the type checker. Additionally, the TypeScript compiler was one of the largest open-source codebases that Microsoft had ever published at the time of its release, and its GitHub repository has consistently been one of the most active on the entire platform, regularly appearing in GitHub's top 10 most-contributed-to repositories.