D3.js Data Visualization Library

D3.js (Data-Driven Documents) is a free and open-source JavaScript library for producing dynamic, interactive data visualizations in web browsers. Created by Mike Bostock (a former visualization lead at The New York Times), Vadim Ogievetsky, and Jeffrey Heer in 2011, D3 has become the most widely used data visualization library for the web, used by The New York Times, NASA, and many data journalism outlets. D3 was the successor to Protovis. Key features: data-driven: D3 binds data to DOM elements, enabling visual transformations as data changes. The data join pattern (selection.data()) enters, updates, and exits elements based on data changes. Selections: query and manipulate DOM elements with a jQuery-like API (d3.select, d3.selectAll). Selections support method chaining for concise code. Scales: map data values to visual properties. Linear, logarithmic, ordinal, band, point, and time scales with configurable domains and ranges. Axes: automatic axis generation (d3.axisBottom, d3.axisLeft) with ticks, labels, and formatting. Shapes: SVG path generators for lines, areas, arcs, pies, chords, links, symbols, and stacks. Layouts: algorithms for specific chart types including treemaps, force-directed graphs, Sankey diagrams, dendrograms, and histograms. Geographic: projections (Mercator, orthographic, conic), path generation, and GeoJSON/TopoJSON support for maps. Zoom and pan. Drag behavior. Force simulation for physics-based layouts. Transitions: animated transitions between states with easing functions (d3.transition, d3.easeCubic). Interactivity: event handling, brushing, tooltips, and cross-filtering. Modular: D3 v5+ is split into over 30 independent micromodules (d3-scale, d3-shape, etc.). SVG and Canvas rendering. JavaScript. ISC.