What means <$_> in js

Answer 1

I found this page that seems to explain it pretty well. Good luck! 😁

https://www.thoughtco.com/and-in-javascript-2037515

Answer 2

this is the sentence that I don't understand:
<$_> must have exactly one child, which must be a string"Да":
it is from JS drawing and anaimation
a confirmation for finishing the project(task)