Refactor code, split routes, change url in backend and update in frontend. Still have bugs, infinite loading after signup?

backend/controllers/product.js

@@ -0,0 +1,70 @@
+const db = require("../utils/database");
+
+exports.addToFavorite = (req, res) => {
+  const { userID, productsID } = req.body;
+
+  // Use parameterized query to prevent SQL injection
+  db.execute(
+    "INSERT INTO Favorites (UserID, ProductID) VALUES (?, ?)",
+    [userID, productsID],
+    (err, result) => {
+      if (err) {
+        console.error("Error adding favorite product:", err);
+        return res.json({ error: "Could not add favorite product" });
+      }
+      res.json({
+        success: true,
+        message: "Product added to favorites successfully",
+      });
+    }
+  );
+};
+
+//Get all products
+exports.getAllProducts = (req, res) => {
+  const query = "SELECT * FROM Product";
+  db.execute(query, (err, data) => {
+    if (err) {
+      console.error("Error finding user:", err);
+      return res.status(500).json({
+        found: false,
+        error: "Database error occurred",
+      });
+    }
+    res.json({
+      success: true,
+      message: "Product added to favorites successfully",
+      data,
+    });
+  });
+};
+
+// db_con.query(
+//   "SELECT ProductID FROM product WHERE ProductID = ?",
+//   [productID],
+//   (err, results) => {
+//     if (err) {
+//       console.error("Error checking product:", err);
+//       return res.json({ error: "Database error" });
+//     }
+
+//     if (results.length === 0) {
+//       return res.json({ error: "Product does not exist" });
+//     }
+//   },
+// );
+
+// db_con.query(
+//   "INSERT INTO Favorites (UserID, ProductID) VALUES (?, ?)",
+//   [userID, productID],
+//   (err, result) => {
+//     if (err) {
+//       console.error("Error adding favorite product:", err);
+//       return res.json({ error: "Could not add favorite product" });
+//     }
+//     res.json({
+//       success: true,
+//       message: "Product added to favorites successfully",
+//     });
+//   },
+// );