Area.svelte component

<!--
  @component
  Generates an SVG area shape.
 -->
<script>
  import { getContext } from 'svelte';

  const { data, xGet, yGet, xScale, yScale, extents } = getContext('LayerCake');

  /**
   * @typedef {Object} Props
   * @property {string} [fill='#ab00d610'] - The shape's fill color. This is technically optional because it comes with a default value but you'll likely want to replace it with your own color.
   */

  /** @type {Props} */
  let { fill = '#ab00d610' } = $props();

  let path = $derived(
    'M' +
      $data
        .map((/** @type {object} */ d) => {
          return $xGet(d) + ',' + $yGet(d);
        })
        .join('L')
  );

  /**  @type {string} **/
  let area = $derived.by(() => {
    const yRange = $yScale.range();
    return (
      path +
      ('L' +
        $xScale($extents.x ? $extents.x[1] : 0) +
        ',' +
        yRange[0] +
        'L' +
        $xScale($extents.x ? $extents.x[0] : 0) +
        ',' +
        yRange[0] +
        'Z')
    );
  });
</script>

<path class="path-area" d={area} {fill}></path>