A D3.js smiley face uses SVG primitives—circles, rectangles, and an arc path—to draw a yellow head, eyes, moving eyebrows, and a mouth. The animation repeatedly translates the eyebrow group up and down via chained `transition().duration()` calls, demonstrating DOM manipulation. The code constructs the face from scratch using D3’s `select`, `append`, and `attr` methods, and computes the mouth’s shape with the `arc` helper, all rendered in an SVG canvas.