Make app composable

Here are the changes I think need to be made to app and h to make sure that apps can be composed over each other. These features will also allow hyperapps to play nicely with independent, non-hyperapp components.

1

app#render() should not try to createElement when node is an element:

const isElement = (node) => node instanceof window.HTMLElement

2

h() should skip elements. If isElement, return “tag”

3

app() should return root.

4

render should check for root existence in DOM before trying to render (making un-mounted apps less of a burden). When an app.root is added to the DOM by a parent app, a hook should fire onAppend. When removed from the DOM, a hook should fire, onRemove. root should be upgraded to a node but should not be mounted to the DOM automatically.

Let’s discuss 😃

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I can probably create the PR this weekend if you’re interested.

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@jbucaran I think it’s exactly what I intended. You may want to adopt the tests I used: https://github.com/hyperapp/hyperapp/pull/151/files to verify.