Solution

src/App.tsx

@@ -1,7 +1,35 @@
 import React from 'react';
 
-export const App: React.FC = () => (
-  <div className="App">
-    <p className="App__message">The last pressed key is [Enter]</p>
-  </div>
-);
+export class App extends React.Component {
+  state = {
+    pressedKey: null,
+  };
+
+  componentDidMount() {
+    document.addEventListener('keyup', this.handleKeyPress);
+  }
+
+  componentWillUnmount() {
+    document.removeEventListener('keyup', this.handleKeyPress);
+  }
+
+  handleKeyPress = (event: KeyboardEvent) => {
+    this.setState({ pressedKey: event.key });
+  };
+
+  render() {
+    const { pressedKey } = this.state;
+
+    return (
+      <div className="App">
+        <p className="App__message">
+          {pressedKey ? (
+            `The last pressed key is [${pressedKey}]`
+          ) : (
+            'Nothing was pressed yet'
+          )}
+        </p>
+      </div>
+    );
+  }
+}