Comparing to vanilla JS provides a good benchmark as to how much the cost is to use a particular library. To provide an example, the Angular team has claimed in talks a few months ago that Angular 2's performance is already close to pure JS for rendering large numbers of DOM elements (I hesitate to say anything about how complex the trees are since I don't remember the details) - profiling is built into the repository itself.
This would cast doubts on some of the theoretic claims on the React docs, at least for mobile.
This would cast doubts on some of the theoretic claims on the React docs, at least for mobile.