Fork of Template Enter, exit and update
This example demonstrates the D3 enter, update, and exit pattern for SVG circles. It creates six circles bound to an array of objects, with a scaleOrdinal mapping object types to blue or red fill colors. The render function appends missing elements on enter and removes extra ones on exit using chained data joins. The code uses d3.select, d3.range, and scaleOrdinal from d3.v7, with all rendering performed directly in SVG.