I recently had a chance to finish up a major refactor of the codebase for BFDLang (Bureaucratic Form Design Language), a hefty (and now Turing-complete) language for describing, well, bureacratic forms to web documents. I work at an insurance company, and BFDLang gives the administrative staff the power to describe a form in a spreadsheet and immediately see what it would look like as a web document; it's a powerful, in-house no-code solution for them backed by a ton of code, mostly written by myself and two junior developers. The refactor was huge, and complicated, and I couldn't have done it with JavaScript. TypeScript saved me weeks of work.