TypeScript is a superset of JavaScript: JavaScript syntax is also TypeScript syntax, extended with annotations, interfaces and generics. Microsoft released version 0.8 in October 2012; its designer, Anders Hejlsberg, also created Turbo Pascal and C#. In August 2025 TypeScript overtook Python and JavaScript as the most used language on GitHub 29 (Octoverse 2025). Runtime semantics (scopes, prototypes, the event loop) belong to JavaScript; this section covers what types buy you, the 6.0 and 7.0 compilers, their internals and the tools that run .ts files.