I think the issue is that the arrays are allowed to have holes: test = new Array(2) -> Array [ <2 empty slots> ] test[1] = true -> true t

I think the issue is that the arrays are allowed to have holes: test = new Array(2) -> Array [ <2 empty slots> ] test[1] = true -> true test.length -> 2 test[0] -> undefined test[3] -> undefined test.some(x => x) -> true delete test[1] -> true test.some(x => x) -> false