diff --git a/webview-sample/media/jsconfig.json b/webview-sample/media/jsconfig.json
index ab5497f1..3a2cf036 100644
--- a/webview-sample/media/jsconfig.json
+++ b/webview-sample/media/jsconfig.json
@@ -3,6 +3,8 @@
 		"module": "commonjs",
 		"target": "es2020",
 		"jsx": "preserve",
+		"checkJs": true,
+		"strict": true,
 		"strictFunctionTypes": true,
 		"lib": [
 			"dom"
diff --git a/webview-sample/media/main.js b/webview-sample/media/main.js
index 2eb6cff1..cea17c6e 100644
--- a/webview-sample/media/main.js
+++ b/webview-sample/media/main.js
@@ -1,18 +1,19 @@
 // This script will be run within the webview itself
 // It cannot access the main VS Code APIs directly.
+
 (function () {
     const vscode = acquireVsCodeApi();
 
-    const oldState = vscode.getState();
+    const oldState = /** @type {{ count: number} | undefined} */ (vscode.getState());
 
-    const counter = document.getElementById('lines-of-code-counter');
+    const counter = /** @type {HTMLElement} */ (document.getElementById('lines-of-code-counter'));
     console.log('Initial state', oldState);
 
     let currentCount = (oldState && oldState.count) || 0;
-    counter.textContent = currentCount;
+    counter.textContent = `${currentCount}`;
 
     setInterval(() => {
-        counter.textContent = currentCount++;
+        counter.textContent = `${currentCount++} `;
 
         // Update state
         vscode.setState({ count: currentCount });
@@ -33,7 +34,7 @@
         switch (message.command) {
             case 'refactor':
                 currentCount = Math.ceil(currentCount * 0.5);
-                counter.textContent = currentCount;
+                counter.textContent = `${currentCount}`;
                 break;
         }
     });