Add React

e.jsx

@@ -0,0 +1,21 @@
+class E extends React.Component {
+  state = {
+    e: "e"
+  };
+
+  componentDidMount() {
+    window.setInterval(
+      () =>
+        this.setState(state => ({
+          e: state.e + "e"
+        })),
+      100
+    );
+  }
+
+  render() {
+    return <div style={{ background: "#eeeeee" }}>{this.state.e}</div>;
+  }
+}
+
+ReactDOM.render(<E />, document.body);