[DCoder]

> Every JS code is a valid TS, since TS is a superset of JS.

There are still cases where you'll need to sprinkle <any>. For example:

    var state = { foo: 1 };
    if(something) {
      state.bar = 2;
    }

is valid JS, but the TS compiler will complain that `state` does not have a member named `bar`.

[addicted]

The TS compiler will complain but still generate working JS code, so you don't lose anything.

[DCoder]

But the compiler's output will be polluted with these false positives, making it harder to see actual errors. (Also, there's a compiler flag to prevent codegen on error, which comes in handy sometimes.)