Comment by dirtyaura

I think Mike Bostock's (the author of D3) tutorials are really high quality too. https://github.com/mbostock/d3/wiki/Tutorials

However, once you dive a bit deeper with selections and nesting, there are some things that are not immediately obvious how to structure. For example, when we implemented small multiple visualization, figuring out the best way to structure enter and update sets for nested data took a few attempts.