improve browser support (#2693)

.changeset/stupid-beans-travel.md

@@ -0,0 +1,5 @@
+---
+'gitbook': patch
+---
+
+Avoid errors on legacy browsers

packages/gitbook/src/components/Ads/Ad.tsx

@@ -44,6 +44,10 @@ export function Ad({
             return;
         }
 
+        if (typeof IntersectionObserver === 'undefined') {
+            return;
+        }
+
         const observer = new IntersectionObserver(
             ([entry]) => {
                 if (entry.isIntersecting) {

packages/gitbook/src/components/hooks/useScrollActiveId.ts

@@ -18,6 +18,10 @@ export function useScrollActiveId(
     React.useEffect(() => {
         setActiveId(null);
 
+        if (typeof IntersectionObserver === 'undefined') {
+            return;
+        }
+
         const onObserve: IntersectionObserverCallback = (entries) => {
             /**
              * We need to keep track of all the sections that are intersecting

packages/gitbook/src/components/utils/ZoomImage.tsx

@@ -63,7 +63,10 @@ export function ZoomImage(
             }
         };
 
-        mediaQueryList.addEventListener('change', onChange);
+        if ('addEventListener' in mediaQueryList) {
+            mediaQueryList.addEventListener('change', onChange);
+        }
+
         if (imgRef.current) {
             resizeObserver?.observe(imgRef.current);
         }
@@ -75,7 +78,9 @@ export function ZoomImage(
 
         return () => {
             resizeObserver?.disconnect();
-            mediaQueryList.removeEventListener('change', onChange);
+            if ('removeEventListener' in mediaQueryList) {
+                mediaQueryList.removeEventListener('change', onChange);
+            }
         };
     }, [imgRef, width]);