I'm the author. Thanks for pointing this out.

I completely agree with your premise. JavaScript and the browser represent the quintessential modern authoring platform.

I actually wanted to write more about JavaScript, but the problem was that there were fewer cohesive, codified sources to cite than I expected. When writing about this kind of historical narrative, the first issue is always whether there are books you can cite.

JS has undergone organic changes along with the turbulent history of the web itself, but there's no clearly organized history of those changes.(To be more precise, it's not that there are none, but rather that the web environment was so fragmented in its early days, and each piece had its own history. Describing all of it would have required too much time) There is Allen Wirfs-Brock and Brendan Eich's 'JavaScript: The First 20 Years,' but it's so lengthy that I couldn't read all of it, so I had to cite only what I had actually read. That's why I ended up cutting a lot of the JS content. I completely agree with your point, but I hope you understand it was a matter of length constraints.