I tried to learn D3 over the weekend. Observable was one of the worst experiences I have ever had with code examples. Every other line is riddled with console output, which makes it hard to take in the example as a whole. Downloading and modifying the example is even worse. It gives you the compiled output of their GUI coding tool.

I ended up using plotly's libraries that are built on top of D3, and it really made me appreciate how much work they put into making it so easy to use.