Rendering five circles in an SVG via a React-started D3 v5 data join, this example demonstrates enter, update, and exit selections over time. It uses `d3.select` to manage the SVG, `d3.range` to generate an array of objects, and `d3.scaleOrdinal` to map domain values like "baseball" and "cube" to fill colors. After two timed `setTimeout` calls, one circle exits with a thick black stroke while another updates its fill from white to dark green.