The aim of hydratation is to avoid trashing out of existing DOM rendered by SSR, but use them
and attach eventual event listeners (like a regular patch pass).
Hydratation would happen at the app level and at the first render. Basically it needs a way to
know that some part of the DOM tree is something to patch so it does not have to mount.
Before going on, some terminology:
- The
rootis the root DOM node generated by HyperApp, the toplevel DOM element. - The
hostis the DOM node that will hold theroot, it's currently defined asapp.root.