This example demonstrates how to create custom color and size legends for D3 visualizations. The color legend displays four categorical fruits using a d3.scaleOrdinal with distinct color ranges, while the size legend uses d3.scaleSqrt to map numeric values from 0 to 10 to circle radii. Both legends are built using reusable functions with enter/merge/exit patterns, rendering SVG groups with circles and text labels. The code uses D3 v5 selection methods and scales to position legend items with configurable spacing and text offsets.