A D3 slider demonstrates a draggable handle on a horizontal track, showing how a single numeric value can be changed through direct manipulation. The code uses an SVG line for the track and a circle for the handle, with the drag behavior updating the circle’s `cx` attribute based on the pointer’s x-coordinate. The handle’s position is clamped between the track’s endpoints using a ternary expression, and the `d3.behavior.drag` API handles the drag events. The example renders entirely with SVG, and the interaction logic is implemented in plain D3 without additional libraries.