cors for vercel

allowCors.js

@@ -0,0 +1,23 @@
+const allowCors = fn => async (req, res) => {
+    res.setHeader('Access-Control-Allow-Credentials', true)
+    res.setHeader('Access-Control-Allow-Origin', '*')
+    // another common pattern
+    // res.setHeader('Access-Control-Allow-Origin', req.headers.origin);
+    res.setHeader('Access-Control-Allow-Methods', 'GET,OPTIONS,PATCH,DELETE,POST,PUT')
+    res.setHeader(
+      'Access-Control-Allow-Headers',
+      'X-CSRF-Token, X-Requested-With, Accept, Accept-Version, Content-Length, Content-MD5, Content-Type, Date, X-Api-Version'
+    )
+    if (req.method === 'OPTIONS') {
+      res.status(200).end()
+      return
+    }
+    return await fn(req, res)
+  }
+
+  const handler = (req, res) => {
+    const d = new Date()
+    res.end(d.toString())
+  }
+
+  module.exports = allowCors(handler)

index.js

@@ -14,12 +14,12 @@ app.listen(port, () => {
     console.log('Express server started at port: 3000');
 });
 app.use(cors());
-app.use( function(req, res, next) {
-    res.header('Access-Control-Allow-Origin', '*');
-    res.header('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE,OPTIONS');
-    res.header('Access-Control-Allow-Headers', 'X-Requested-With, X-HTTP-Method-Override, Content-Type, Accept');
-    next();
-});
+// app.use( function(req, res, next) {
+//     res.header('Access-Control-Allow-Origin', '*');
+//     res.header('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE,OPTIONS');
+//     res.header('Access-Control-Allow-Headers', 'X-Requested-With, X-HTTP-Method-Override, Content-Type, Accept');
+//     next();
+// });
 app.use('/user', userController); 
 app.use('/survey', surveyController);
 app.use('/response', responseController); 

vercel.json

@@ -15,5 +15,16 @@
             "src": "/",
             "dest": "ui/build/index.html"
           }
-    ]
+    ],
+    "headers": [
+        {
+          "source": "/(.*)",
+          "headers": [
+            { "key": "Access-Control-Allow-Credentials", "value": "true" },
+            { "key": "Access-Control-Allow-Origin", "value": "*" },
+            { "key": "Access-Control-Allow-Methods", "value": "GET,OPTIONS,PATCH,DELETE,POST,PUT" },
+            { "key": "Access-Control-Allow-Headers", "value": "X-CSRF-Token, X-Requested-With, Accept, Accept-Version, Content-Length, Content-MD5, Content-Type, Date, X-Api-Version" }
+          ]
+        }
+      ]
   }