That's brilliant! I would have never thought of that myself!

dope!, this was my first thought but it felt too easy and I doubted mysefl.

Clever replacement trick and list comprehension!!

You did it like a Boss!

im a complicated person

it is like declaring multiple variables at once, i.e. let a, b, c = 5

Amazing display of string method stacking, I did not know that was possible, great work!

i guess there is no proper way to do this using TimeSpan.ToString formatting directly ?
...maybe that's the "catch" of this kata

Let the compiler optimise that.

I wrote the same code but for some reason my test kept insisting I always returned 0 xD I even tried just returning elements of the input but it still said 0 every time.

I disagree with "shortest runtime == best", in general. Legibility and maintainability are often more important. Runtime (and memory space) optimizations can be important in some cases, but you need to have a look where it makes most sense and try to avoid premature optimization.

Simply amazing! And still quite legible for a one-liner. Though, in production code, I would prefer to have the clipping factored out in its own function.

what does the $ sign mean?

Why Object.assign(this, {firstName}) is used here instead of this.firstName=firstName? I haven't seen this method mentioned in a JavaScript book.

upd: copies into an object... Genius!