Two custom legends demonstrate the general update pattern under special cases using D3 v5. The color legend maps fruit names to ordinal colors, while the size legend uses a square-root scale for circle radii. Both legends are built with reusable modules that leverage selection joins, enter/merge/exit methods, and explicit spacing. The code uses d3.scaleOrdinal, d3.scaleSqrt, and the .call() method to attach the legends to an SVG.