Fork of Template Enter, exit and update
A D3.js animation demonstrates how enter, update, and exit selections handle changing data. Six blue circles appear in a row, then one circle is removed after two seconds, and the first remaining circle turns red after four seconds. The code uses `selection.selectAll`, `.data()`, `.enter()`, `.exit()`, and `.transition()` from D3 v7, with `scaleOrdinal` mapping types to colors. SVG elements are rendered and animated directly on a blank canvas.