I am seeing code like:

(0, _classCallCheck3.default)(this, BaseCommand);

I'm guessing after the original source was ran through babel and stuff like that? What is this ()() construct? I understand the second parentheses as arguments for a function invocation, which makes (0, _classCallCheck3.default) I guess a function?

I've never seen this syntax before - what does it mean? What is the first bracket doing in raw javascript and how does the javascript interpreter know what to do with it?!!