support custom sheet and create headers

google-script.js

@@ -24,21 +24,32 @@ function doPost(e) {
       sheet = ss.getActiveSheet();
     }
     
-    // 2. Get headers
-    var lastCol = sheet.getLastColumn();
     var headers = [];
+    
+    // 2. If sheet is brand new (no rows), create headers first
+    if (sheet.getLastRow() === 0) {
+      // Extract keys from data, excluding 'sheetName' which is a control parameter
+      headers = Object.keys(data).filter(function(key) {
+        return key !== "sheetName";
+      });
+      sheet.appendRow(headers);
+    } else {
+      // 3. If sheet already exists, get existing headers from the first row
+      var lastCol = sheet.getLastColumn();
       if (lastCol > 0) {
         headers = sheet.getRange(1, 1, 1, lastCol).getValues()[0];
-    }
-
-    // 3. If sheet is empty, set headers from JSON keys
-    if (headers.length === 0 || headers[0] === "") {
-      headers = Object.keys(data);
+      } else {
+        // Fallback for edge cases where lastRow > 0 but lastCol is 0
+        headers = Object.keys(data).filter(function(key) {
+          return key !== "sheetName";
+        });
         sheet.appendRow(headers);
       }
+    }
     
-    // 4. Map data to headers
+    // 4. Map data to the determined headers
     var row = headers.map(function(header) {
+      // data[header] might be undefined for some rows if schema changes
       return data[header] !== undefined ? data[header] : "N/A";
     });