Two legends for ordinal and quantitative scales demonstrate D3's general update pattern with special cases. The color legend maps fruit categories to red, yellow, green, and orange circles using `d3.scaleOrdinal`, while the size legend uses `d3.scaleSqrt` to encode values 0–10 as circle radii, filtering out zero and reversing ticks. Both legends use reusable functions (`colorLegend` and `sizeLegend`) with enter, merge, and exit selections, rendering as SVG. The code relies on D3 v5 APIs including `selection.enter`, `selection.merge`, and `selection.exit`.