Access to XMLHttpRequest at ‘http://localhost:8080/’ from origin ‘http://localhost:3000’ has been blocked by CORS policy

Full error: “Access to XMLHttpRequest at ‘http://localhost:8080/api/tutorials’ from origin ‘http://localhost:3000’ has been blocked by CORS policy: Response to preflight request doesn’t pass access control check: No ‘Access-Control-Allow-Origin’ header is present on the requested resource.”

On the frontend I am using NuxtJS. I am sending a simple post request at the node server hosted on localhost:3000, but it’s giving me this error even though I am using CORS in my app. The request is for inserting data in the mongodb database.

On the node server i.e. localhost:8080, I’ve tried:

var corsOptions = {
  origin: "http://localhost:3000",
};

app.use(cors(corsOptions));

Tried this too but no success:

app.use(function (req, res, next) {
  res.setHeader("Access-Control-Allow-Origin", "*");

  next();
});

Please tell if there is any solution for this error. Thank you.

EDITED:

Here, I am using axios to first create an instance (on the frontend). https://ibb.co/C2ChH5d

These are all the requests that I want to use. https://ibb.co/5TbSHjF

And this is the request that is being made currently(create). https://ibb.co/pPp8rdh

The nodeJS code: https://ibb.co/GFWMQW1

NodeJS code:

const express = require("express");
const bodyParser = require("body-parser");
const cors = require("cors");

const app = express();

require("./app/routes/tutorial.routes")(app);

var corsOptions = {
  origin: "http://localhost:3000",
};

app.options("*", cors());

app.use(cors(corsOptions));

// parse requests of content-type - application/json
app.use(bodyParser.json());

// parse requests of content-type - application/x-www-form-urlencoded
app.use(bodyParser.urlencoded({ extended: true }));

// simple route
app.get("/", (req, res) => {
  res.json({ message: "Welcome to bezkoder application." });
});

// set port, listen for requests
const PORT = process.env.PORT || 8080;
app.listen(PORT, () => {
  console.log(`Server is running on port ${PORT}.`);
});

const db = require("./app/models");
db.mongoose
  .connect(db.url, {
    useNewUrlParser: true,
    useUnifiedTopology: true,
  })
  .then(() => {
    console.log("Connected to the database!");
  })
  .catch((err) => {
    console.log("Cannot connect to the database!", err);
    process.exit();
  });

Answer

Well, the problem was that I was using the API routes before initializing cors(). When I shifted the routes down the app.use(cors(corsOptions)), the problem was solved.