This is nice in theory, but... A user visits site A. To get a cached version of React the following need to be true: 1. A user has to have visited a site, site

This is nice in theory, but... A user visits site A. To get a cached version of React the following need to be true: 1. A user has to have visited a site, site B, with React recently. 2. The site with React needs to be using a publicly available CDN. 3. Site A and Site B must use the same CDN. 4. The versions of React must match exactly. There are already about a dozen alpha/patch/rc versions of the React 15.x.x series alone. In practice, this does not happen very often: https://www.stevesouders.com/blog/2013/03/18/http-archive-jquery/ https://www.stevesouders.com/blog/2013/03/18/http-archive-jq...