Fix JavaScript error when clicking a footnote link.

Author: charles7668

web_src/js/markup/anchors.ts

@@ -6,7 +6,8 @@ const hasPrefix = (str: string): boolean => str.startsWith('user-content-');
 
 // scroll to anchor while respecting the `user-content` prefix that exists on the target
 function scrollToAnchor(encodedId: string): void {
-  if (!encodedId) return;
+  // Ignore the footnote case, as the link is rendered by the backend.
+  if (!encodedId || encodedId.startsWith('fn:') || encodedId.startsWith('fnref:')) return;
   const id = decodeURIComponent(encodedId);
   const prefixedId = addPrefix(id);
   let el = document.querySelector(`#${prefixedId}`);
@@ -55,6 +56,7 @@ export function initMarkupAnchors(): void {
 
     for (const a of markupEl.querySelectorAll<HTMLAnchorElement>('a[href^="#"]')) {
       a.addEventListener('click', (e) => {
+        console.log(e.currentTarget)
         scrollToAnchor((e.currentTarget as HTMLAnchorElement).getAttribute('href')?.substring(1));
       });
     }