Merge pull request #89 from thisispaul/master

Author: squirrelsquirrel78

src/Scrollama.js

@@ -43,9 +43,10 @@ const Scrollama = props => {
     }
   }, []);
 
-  const innerHeight = (windowInnerHeight || window.innerHeight)
+  const isBrowser = typeof window !== "undefined";
+  const innerHeight = isBrowser ? (windowInnerHeight || window.innerHeight) : 0;
 
-  const offsetValue = isOffsetDefinedInPixels 
+  const offsetValue = isOffsetDefinedInPixels
     ? (+offset.replace('px', '') / innerHeight)
     : offset;
 

src/Step.js

@@ -27,7 +27,8 @@ const Step = props => {
     innerHeight,
   } = props;
 
-  const scrollTop = document.documentElement.scrollTop;
+  const isBrowser = typeof window !== "undefined";
+  const scrollTop = isBrowser ? document.documentElement.scrollTop : 0;
   const direction = lastScrollTop < scrollTop ? 'down' : 'up';
 
   const rootMargin = useRootMargin(offset);
@@ -58,7 +59,7 @@ const Step = props => {
     },
     [inViewRef, scrollProgressRef],
   );
- 
+
 
   React.useEffect(() => {
     if (isIntersecting) {