this context: Node or singleton selection?

[mbostock]

Should the this context of property functions be a Node or a singleton selection, as in d3.select(this)? The singleton selection is convenient in some cases, but it does not provide the complete functionality of the W3C DOM API, and extracting the element is a bit awkward: this[0][0].

Also, there are cases where callbacks are associated with individual nodes (such as "mouseover") and other cases where there are multiple nodes (such as the .call method, and non-staggered transition "end"). Maybe it's only in the latter where we use a selection as the this context.

Also, we could shorten the syntax to d3(this) rather than d3.select(this) to make it easier to convert. And this.node() might be clearer than this[0][0].

[mbostock]

Keeping it as a node, for now, so as to minimize overhead and keep it simple.