Really new to React, so forgive me if this is on page 1 of the book...
I've got a small drag and drop sample working in React. I can drag a
<div>
<div>
scrollLeft
scrollLeft
this.setState
accepts a second optional parameter which is callback that runs after the render has completed.
For example,
this.setState({ /* your state */ }, function() {
...
this.refs.yourRef.scrollLeft = /* someValue */;
});