I just finished something similar: http://caines.ca/blog/2018/12/11/a-javascript-to-typescript-conversion-case-study/ http://caines.ca/blog/2018/12/11/a-javascr

I just finished something similar: http://caines.ca/blog/2018/12/11/a-javascript-to-typescript-conversion-case-study/ http://caines.ca/blog/2018/12/11/a-javascript-to-typescript-... We opted to keep it strict (no implicit `any`) through the entire transition but only apply it to ts files, so we are indeed completely free of type errors now. We only have 50 cases of (explicit) `any` in 85K+ LOC and they're in type def files. Let me be the first person you've met to doubt the value of the type system. I do like the in-editor support, but you pay for it with about 25% more code. I'm certainly not advocating undoing it, but I personally wouldn't do it again (though the team has mixed opinions). Just curious: What's your test coverage like?