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One line of TS, then two lines of JS (with a type annotation in one of them)

It’s not even 2 lines:

1. Type definition 2. Chain definition 3. Enqueue definition

Line 1 is fully erased when transpiling, leaving two lines of JavaScript.

But you still had to write it and it's required to get the result, so I don't see any rational for not counting it.

Transpilation does not change the fact that the input is these 3 lines of code in 2 different languages.

Right, and only two of those lines are JavaScript. The type definition is not required to get the result.