Check if window exists

Author: sebmarkbage

packages/react-dom-bindings/src/client/ReactFiberConfigDOM.js

@@ -759,6 +759,12 @@ export function commitTextUpdate(
   textInstance.nodeValue = newText;
 }
 
+const supportsMoveBefore =
+  // $FlowFixMe[prop-missing]: We're doing the feature detection here.
+  enableMoveBefore &&
+  typeof window !== 'undefined' &&
+  typeof window.Node.prototype.moveBefore === 'function';
+
 export function appendChild(
   parentInstance: Instance,
   child: Instance | TextInstance,
@@ -801,10 +807,6 @@ export function appendChildToContainer(
   }
 }
 
-const supportsMoveBefore =
-  // $FlowFixMe[prop-missing]: We're doing the feature detection here.
-  enableMoveBefore && typeof Node.prototype.moveBefore === 'function';
-
 export function insertBefore(
   parentInstance: Instance,
   child: Instance | TextInstance,