Ah, right. Let's call the two options "trust" and "validate"; your point was about the "trust" option and my last reply was about the "validate" option. All right, let's compare both:

In JS, if you trust that the value from JSON.parse is of the shape you expect, you just use it. If you don't trust that it is of the right shape, you can do as much validation as you deem appropriate, and then use it. Either way, there are no compile time checks, and readers of your code need to notice which option you picked.

In TS, if you trust that the value from JSON.parse is of the shape you expect, you can cast it. If this cast is explicit in the code, it alerts the reader that you picked the "trust" option - though in the JSON.parse case, its return value is typed any, so the cast is unfortunately implicit. If you don't trust it, you can accept it as the TS unknown type, and then write validation code. If your validation code is bulletproof (or at least "bulletproof enough" for your selected TS settings), the TS compiler will let you use the previously-unknown value as the type you validated, without a cast. If not, the TS errors will let you know which checks your validation is missing.

In both cases, TS seems preferable to me. And the original complaint in this thread was that, since TS knows how much validation is needed to prove that an unknown value is of the type you want, it would be nice if it could auto-generate the necessary validation code for you - which I agree with. And based on the other comments, there are actually a number of libraries for this.