Render whatever you want, it's called with an object with the following properties:
registerContainer(ref)pass to the container's ref prop
registerSticky(ref)pass to the ref prop of whatever node within the container if you want to make it sticky
updateState()update the sticky state manually, this useful if your content is resizable
getStickyOffsets()return all the sticky-able elements' offsets
scrollToIndex(index)scroll to the specific sticky element by index
scrollTo(offset)scroll to the specific offset
The ref-register must be passed to the real DOM node, so if the component is a wrapper uppon DOM node, you need to register it to the underlying DOM node, using innerRef or something like that if provided.
The className to be attached to the element when it's sticky
This feature relies on classList which is not supported below IE10, so it won't take any effect on IE9 or below, you can use onSticky to implement by yourself.