[frontendbeauty]

Correct. If you're already writing a bunch of JavaScript for the client-side, then just think about this approach as migrating some of that client, UI logic to the server.

[CmonDev]

To have two problems instead of one?

[frontendbeauty]

There are already two problems, if you're building a rich client-side web app. Have you done this? If so, you would understand the problem.

[camus2]

but who writes clientside logic before serverside logic ?

[Wilya]

Front-end developers.

Frankly, Node is a way for front-end developers to write server-side code without having to learn too much new stuff.