To hide the side menu in a React Ionic Application, use the following code example in your App.tsx file:

App.tsx

<IonSplitPane contentId="main" when="false">
   <Menu />
   <IonRouterOutlet id="main">
      <Route path="/" exact={true}>
         <Redirect to="/" />
       </Route>
   </IonRouterOutlet>
</IonSplitPane>

 

Ionic - Side Menu Close Button Example Code