The albersUsa projection is one of many D3.js supplied projection objects. You can see the full list of these projections at https://github.com/mbostock/d3/wiki/Geo-Projections.
We don't have space to demonstrate all of these in this book, but a few are worth the effort to demonstrate a couple of TopoJSON concepts. Specifically, we will demonstrate the rendering of a map of the countries of the world, sourced from TopoJSON, and projected onto both flat and spherical surfaces.
For data in these examples, will use the
world-110m.json data file provided with the TopoJSON data library source code available at https://gist.githubusercontent.com/d3byex/65a128a9a499f7f0b37d/raw/176771c2f08dbd3431009ae27bef9b2f2fb56e36/world-110m.json ...