How to Migrate a Large JavaScript Codebase to TypeScript Incrementally (No Drama, No Rewrites)
Surprising fact: TypeScript adoption has crossed a tipping point — surveys show that over two-thirds of modern front-end projects now include TypeScript in at least part of the codebase. If your large JavaScript repository still avoids types, you’re swimming against the tide — but you don’t need a big rewrite to catch up. Why migrate to TypeScript now: benefits, ROI, and common misconceptions Benefits in plain terms Incremental TypeScript migration delivers faster developer feedback, fewer runtime type errors, and better maintainability. Teams that adopt TypeScript typically report faster onboarding and improved refactor safety — meaningful ROI when measured across a year. Hard numbers (what the data says) Survey data shows over 60% of modern front-end projects include TypeScript in some capacity (ecosystem surveys like State of JS). Industry case studies commonly report a 15–30% reduction in certain classes of runtime bugs after migration to TypeScript and stricter ch...