This example demonstrates two types of legends for mapping data to visual encodings: a color legend for categorical values and a size legend for quantitative values. The color legend displays circles colored via a d3.scaleOrdinal mapping fruit names to colors, while the size legend uses d3.scaleSqrt to represent numeric ticks as varying circle radii. Both legends are rendered as SVG groups with d3-selection, using join patterns to update circle and text elements. The code is built with React and D3 v6, with the legends generated procedurally from scales rather than external data.