hola.js

const express = require("express");
const app = express();
const port = process.env.PORT || 3000;

app.get("/", (req, res) => {
  res.sendFile("index.html", { root: __dirname });
});

app.get("/user/signin/callback", (req, res) => {
  const { query } = req;
  const { code } = query;
  if (!code) {
    return res.send({
      success: "false",
      message: "Error, no code"
    });
  }
  res.send(code);
});

app.listen(port, () => console.log(`Example app listening on port ${port}!`));