[datasert]

We have been using typescript in large scale JS project with 15-20 library modules and 7-8 product modules. I cannot think of building such product without typescript. When we compile all libraries and products and see no TS errors, we know at least that we are referring to correct properties, and wiring the shape correctly.

Typescript has bunch of "clever" things but you don't have to use it. We probably use 30-40% of TS features and that is more than sufficient for us. With that said, here is what I think about your questions.

1. Agree, and it is not any better without TS either. In case, a library is not compiling with your TS version, we ignore the error, put a FIXME there and remove the "ignore" sometime later

2. Yes but that is not TS problem. Without TS it is even worse.

3. Agree sometimes, we get so complicated errors. We search around and see if any smart people have figured what that means. If not, ignore and move on with a FIXME

4. Since many years, we are not writing any JS which doesn't need transpiling. If not TS, you would be using babbel or some other tool most of the time anyways so we haven't this to be an issue.

[orangecat]

We probably use 30-40% of TS features and that is more than sufficient for us

Exactly. Some people seem to have the idea that you have to spend weeks writing esoteric type definitions before TS will work for you, which is just not true. You can get a large portion of the benefits with very little additional work, often just adding types for function arguments. (In many cases those types can replace comments that were trying to convey that same information, with the advantage that they won't get out of sync with the code). And for code that intentionally takes advantage of dynamic typing, it's perfectly fine to slap "any" on it rather than trying to come up with a bunch of clever types.