This example demonstrates two reusable legend components in D3 v5: a color legend and a size legend. The color legend maps categorical domain values like ‘apple’ and ‘lemon’ to distinct fill colors using `scaleOrdinal`, while the size legend visualizes a continuous numeric range with `scaleSqrt`, rendering circles whose radii grow proportionally. Both legends use SVG groups and the enter–update–exit pattern to bind data, with ticks and text labels positioned via transform attributes. The size legend filters out zero and reverses tick order for clarity.