A smiley face is drawn in SVG using React and D3.js, with a yellow circular head, black outline, two eyes, and a curved mouth arc. The face is centered on a 960x500 canvas, with the head radius calculated from the height and stroke width. The eyes are positioned using offsets from the center, and the mouth is generated using D3's `arc` function to create a semi-circular path with specified inner and outer radii. The code demonstrates a declarative React component structure for SVG rendering.