return error when register user with used email:

mongoDB.js

@@ -50,8 +50,12 @@ const getDB = new Promise((resolve, reject) => {
 
         DB.newUser = (userInformation)=>{
             return DB.usersCol.insertOne(userInformation).catch((err)=>{
+                if (err.name === 'MongoError' && err.code === 11000) {
+                    // Duplicate username
+                    return "User already exists";
+                }
                 console.log(err);
-                return false;
+                return "System Error";
             });
         };