[components/MDX][s]: minor changes - observer hook

site/components/MdxContent.js

@@ -26,6 +26,4 @@ const MdxContent = ({ body }) => {
   return <Component components={customComponents} />;
 };
 
-// prevent rerendering of the component if it's props don't change
+export default MdxContent;
-// i.e. re-render only when the observer is set
-export default React.memo(MdxContent);

site/hooks/useHeadingsObserver.js

@@ -1,5 +1,4 @@
-import { useState, useEffect } from 'react';
+import { useState, useEffect } from "react";
-
 
 /* Creates an Intersection Observer to keep track of headings intersecting
  * a section of the viewport defined by the rootMargin */
@@ -13,7 +12,7 @@ const getIntersectionObserver = (callback) => {
     {
       root: null,
       threshold: 0.55,
-      rootMargin: "-65px 0% -85% 0%" // 65px is a navbar height
+      rootMargin: "-65px 0% -85% 0%", // 65px is a navbar height
     }
   );
 };
@@ -24,7 +23,7 @@ const useHeadingsObserver = () => {
 
   /* Runs only after the first render, in order to preserve the observer
    * between component rerenderings (e.g. after activeHeading change). */
-  useEffect((() => {
+  useEffect(() => {
     const observer = getIntersectionObserver((entry) => {
       if (entry.isIntersecting) {
         setActiveHeading(entry.target.id);
@@ -32,26 +31,30 @@ const useHeadingsObserver = () => {
     });
     setObserver(observer);
 
-    return observer.disconnect();
+    return () => {
-  }), [])
+      observer.disconnect();
+    };
+  }, []);
 
   /* On initial render activeHeading will be `null`, since the observer
    * has not been instantiated yet. However, we still want to highlight
    * the current heading in the ToC based on the current url. */
   useEffect(() => {
     if (!activeHeading) {
-      return
+      return;
     }
 
-    const tocLink = document.querySelector(`.toc-link[href="#${activeHeading}"]`)
+    const tocLink = document.querySelector(
+      `.toc-link[href="#${activeHeading}"]`
+    );
     tocLink.classList.add("active");
 
     return () => {
-      tocLink.classList.remove("active")
+      tocLink.classList.remove("active");
-    }
+    };
-  }, [activeHeading])
+  }, [activeHeading]);
 
   return observer;
-}
+};
 
 export default useHeadingsObserver;