fixed flow type error (reference: verekia/js-stack-from-scratch#249)

Pomodoro Clock (with React + Redux)
htbkoo · Dec 20, 2017 · d594609 · d594609
1 parent 89b52bc
commit d594609
Showing 1 changed file with 6 additions and 1 deletion.
diff --git a/src/index.js b/src/index.js
@@ -5,5 +5,10 @@ import './index.css';
 import App from './App';
 import registerServiceWorker from './registerServiceWorker';
 
-ReactDOM.render(<App/>, document.getElementById('root'));
+const ROOT_CONTAINER_SELECTOR = 'root';
+const rootEl = document.getElementById(ROOT_CONTAINER_SELECTOR);
+if (!(rootEl instanceof Element)) {
+    throw new Error('invalid type');
+}
+ReactDOM.render(<App/>, rootEl);
 registerServiceWorker();