Patch: "Reloading the registration page should warn about data loss" (#8377)

Author: yaya-usman

src/components/structures/auth/Registration.tsx

@@ -139,8 +139,21 @@ export default class Registration extends React.Component<IProps, IState> {
 
     componentDidMount() {
         this.replaceClient(this.props.serverConfig);
+        //triggers a confirmation dialog for data loss before page unloads/refreshes
+        window.addEventListener("beforeunload", this.unloadCallback);
     }
 
+    componentWillUnmount() {
+        window.removeEventListener("beforeunload", this.unloadCallback);
+    }
+
+    private unloadCallback = (event: BeforeUnloadEvent) => {
+        if (this.state.doingUIAuth) {
+            event.preventDefault();
+            event.returnValue = "";
+            return "";
+        }
+    };
     // TODO: [REACT-WARNING] Replace with appropriate lifecycle event
     // eslint-disable-next-line
     UNSAFE_componentWillReceiveProps(newProps) {