Two updatable bar charts demonstrate how D3.js v5 charts can be modified after initial rendering. The example uses JavaScript closures to create reusable chart functions, with `select` and `max` imported from D3. The charts display arrays of running miles and temperature data, rendered as SVG rectangles with animated transitions. The `transition().duration(900)` API animates updates to data, width, and fill color, while `.data()` and `.fillColor()` methods allow property changes at runtime.