Bertin.js

Mimics GIS software by allowing stacking of multiple map layers (e.g., choropleth, bubble, graticule) in a defined hierarchy, reducing code complexity for complex visualizations.

Supports numerous thematic map styles out-of-the-box, including choropleths, typology maps, proportional symbols, dot density, and cartograms, as shown in the extensive examples.

Designed for seamless use in Observable notebooks and Quarto documents, enabling reproducible research and data journalism with geospatial data.

Integrates with D3.js projections, offering custom options like 'Polar' or 'Spilhaus', and supports globe views for certain layer types.

The update() function allows modification of specific map elements (e.g., fill, stroke) without redrawing the entire map, optimizing performance for interactive tweaks.