Update vanillaJs.md

frontend/vanillaJs.md

@@ -240,6 +240,16 @@ const applyMask = (mask, canvas, result) => {
 ```
 ### Iframe
 
+-  Embed apps in iframe should consider SameSite. ([reference](https://medium.com/%E7%A8%8B%E5%BC%8F%E7%8C%BF%E5%90%83%E9%A6%99%E8%95%89/%E5%86%8D%E6%8E%A2%E5%90%8C%E6%BA%90%E6%94%BF%E7%AD%96-%E8%AB%87-samesite-%E8%A8%AD%E5%AE%9A%E5%B0%8D-cookie-%E7%9A%84%E5%BD%B1%E9%9F%BF%E8%88%87%E6%B3%A8%E6%84%8F%E4%BA%8B%E9%A0%85-6195d10d4441))
+
+```javascript
+// server-side
+res.cookie("name", value, {
+    samSite: "None",
+    secure: true,
+});
+```
+
 - Make iframe content bigger
 
 ```css
@@ -460,4 +470,4 @@ const Recorder = (() => {
 })();
 
 export default Recorder;
-```
+```