rd3-04-slice.js

class Slice extends React.Component {
  render() {
    let {value, fill, innerRadius = 0, outerRadius} = this.props;
    // https://github.com/d3/d3/wiki/SVG-Shapes#arc
    let arc = d3.svg.arc()
      .innerRadius(innerRadius)
      .outerRadius(outerRadius);
    return (
      <path d={arc(value)} fill={fill} />
    );
  }
}