adds option to render markdown headings with anchor links

scm-ui-components/packages/ui-components/src/MarkdownHeadingRenderer.js

@@ -0,0 +1,35 @@
+// @flow
+import * as React from "react";
+
+/**
+ * Adds anchor links to markdown headings.
+ *
+ * @see <a href="https://github.com/rexxars/react-markdown/issues/69">Headings are missing anchors / ids</a>
+ */
+
+type Props = {
+  children: React.Node,
+  level: number
+};
+
+function flatten(text: string, child: any) {
+  return typeof child === "string"
+    ? text + child
+    : React.Children.toArray(child.props.children).reduce(flatten, text);
+}
+
+/**
+ * Turns heading text into a anchor id
+ *
+ * @VisibleForTesting
+ */
+export function headingToAnchorId(heading: string) {
+  return heading.toLowerCase().replace(/\W/g, "-");
+}
+
+export default function MarkdownHeadingRenderer(props: Props) {
+  const children = React.Children.toArray(props.children);
+  const heading = children.reduce(flatten, "");
+  const anchorId = headingToAnchorId(heading);
+  return React.createElement("h" + props.level, {id: anchorId}, props.children);
+}