Here's a sampler pack from my old site:
https://github.com/agm1984/adammackintosh-dot-net-ssr/blob/master/src/route_animations.js
https://github.com/agm1984/adammackintosh-dot-net-ssr/blob/master/src/Routes.js
Code looks a little savage, but could be useful for scavenging useful parts.