Move a JavaScript module to strict TypeScript one flag at a time, with the compiler and your tests as the gate

Fri, 30 Oct 2026 11:05:00 +0000

A 400-line JavaScript module has to become TypeScript, and the obvious plan is to rename every file to .ts, flip strict on and let an agent grind through the errors. That plan produces a diff nobody can review. Hundreds of errors arrive at once, the fastest way to silence them is any or a cast, and somewhere in the pile a “fix” quietly changes what the function returns.

Strict-Mode on Tokenise

Move a JavaScript module to strict TypeScript one flag at a time, with the compiler and your tests as the gate