I am using mongodb, with NodeJS ORM, mongoose, A modelis shown below

const mongoose = require('mongoose');

const userFeedbackIdsSchema = new mongoose.Schema({
    feedbackId: { type: String, unique: true },
    userId: { type: mongoose.Schema.Types.ObjectId, ref: 'User', required: true },
    // other fields...
  });
  
  module.exports = mongoose.model('UserFeedbackIds', userFeedbackIdsSchema);

With following endpoint

 router.post('/generateId', async (req, res) => {
    const { userId } = req.body;
  
    if (!userId) {
      return res.status(400).json({ error: 'User ID is required' });
    }
    let uniqueId;
    let isUnique = false;
  
    while (!isUnique) {
      uniqueId = generateUniqueId(8);
      const existingFeedback = await UserFeedback.findOne({ feedbackId: uniqueId });
      if (!existingFeedback) {
        isUnique = true;
      }
    }
    
    const newFeedback = new UserFeedback({ feedbackId: uniqueId, userId });
    await newFeedback.save();
  
    res.json({ uniqueId });
  })

When I called the endpoint with a dummyvalue,

      const response = await axios.post(`${API_ADDRESS}/users/generateId`, { userId: 'dummytest' });

The following cors error was thrown

Access to XMLHttpRequest at ‘site-address/users/generate-id/’ from origin ‘http://localhost:3000’ has been blocked by CORS policy: No ‘Access-Control-Allow-Origin’ header is present on the requested resource.

I had defined the cors

app.use(cors({
    origin: 'http://localhost:3000', // Allow requests from this origin
    methods: ['GET', 'POST'], // Allow these HTTP methods
    credentials: true // Allow cookies to be sent
  }));

My question is, how come the cors issue was raised; on wrong data value, the issue was resolved once the correct data value was passed.