A smiley face rendered in SVG uses D3.js to animate its eyebrows with a repeating transition. The code selects the SVG via `d3.select`, builds face shapes with `circle` and `rect` elements, and draws the mouth using `d3.arc`. Eyebrows move upward and downward through chained `transition.attr` calls on a group, showing basic DOM manipulation and animation. The face’s blue head, black stroke, and asymmetric eyes are hardcoded, with no external data source.