Clean up useEventEmitter

src/hooks/useEventEmitter.js

@@ -1,3 +1,19 @@
+/*
+Copyright 2019 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
 import {useRef, useEffect} from "react";
 
 // Hook to wrap event emitter on and removeListener in hook lifecycle
@@ -6,19 +22,12 @@ export const useEventEmitter = (emitter, eventName, handler) => {
     const savedHandler = useRef();
 
     // Update ref.current value if handler changes.
-    // This allows our effect below to always get latest handler ...
-    // ... without us needing to pass it in effect deps array ...
-    // ... and potentially cause effect to re-run every render.
     useEffect(() => {
         savedHandler.current = handler;
     }, [handler]);
 
     useEffect(
         () => {
-            // Make sure element supports on
-            const isSupported = emitter && emitter.on;
-            if (!isSupported) return;
-
             // Create event listener that calls handler function stored in ref
             const eventListener = event => savedHandler.current(event);