Why “this” refers to Window in forEach in javascript? [duplicate]

Answer 1

this gets defined using by new, or the object invoking this function, right?

Yes. And in this case, it's forEach that invokes your function. Since no special precautions^[1] are made, it simply passes nothing for this^[2] just like any non-method function call, which will result into the global object as your function is sloppy code^[3].

_{1: Like passing a second argument to forEach, which would be used for this
2: The spec says it should pass undefined
3: Meaning, that it does not use strict mode. In strict code, this would literally really be undefined.}