This is doing the same thing described in the GP of your comment. If 1/few people are building a site so simple that the menu code is in "menu.js", then sure,

This is doing the same thing described in the GP of your comment. If 1/few people are building a site so simple that the menu code is in "menu.js", then sure, separate your code and go about your day. But when 30+ FTEs are building a huge app with lots of tightly interconnected features, then the complexity is there no matter how you architect your code - it's part of the business requirements. Like GGP said, they're different domains, and stuff said about one doesn't necessarily apply to the other.