JavaScript's flexibility is both its strength and its biggest liability. A function that expects a number can silently receive a string, process it incorrectly, and corrupt data downstream — and you won't know until a customer reports a bug.
TypeScript catches these errors at build time, before they reach production. In our experience across 80+ projects, TypeScript reduces production bugs by 30-40% compared to plain JavaScript. That's not a theoretical number — it's measured from actual bug tracking data across our client projects.
The argument against TypeScript — "it's slower to write" — was valid in 2018. Modern TypeScript with good IDE support (VS Code) actually makes you faster through autocompletion, inline documentation, and instant error feedback. You write code slightly differently; you debug 60% less.
For our clients at Ethersofts, TypeScript is non-negotiable on any project expected to last more than 6 months. The type system serves as living documentation — new developers joining the project can understand data shapes and function contracts without reading a separate wiki.