TypeScript
Anders Hejlsberg · 2012
TypeScript is a compiler-layered static typing system for JavaScript. It solves scalability problems in large codebases by enabling early error detection and better tooling — without breaking compatibility. Its mechanism is transpilation, not runtime enforcement. Its biggest win is developer velocity in complex projects — proven by the 8–12× speedup in TypeScript 7.0. Its cost is added complexity and no runtime guarantees.