Two reusable legend components demonstrate the general update pattern in D3 v5 with SVG rendering, using `scaleOrdinal` for fruit colors and `scaleSqrt` for size encoding. The color legend’s static ordinal domain and the size legend’s thresholded tick values show handled special cases, including filtering out zero and reversing tick order. Each legend appends groups, merges enter/update selections, and removes exits, with `d3.selectAll` and explicit `enter().append` for circles and text.