This example demonstrates how to add and remove data values from a bar chart in real time. Clicking the "Add a new data value" button pushes a randomly generated number onto a dataset, while clicking "Remove a data value" shifts the first element off the array. The SVG bars and text labels update with smooth transitions using D3’s `transition` and `duration` methods, with the x-scale domain recalculated via `d3.scaleBand` and `d3.range` to reflect the changing data length.