this is the whole idea:

const express = require("express")
const app = express()

const router = require("./router")

app.use(express.static("public"))
app.use(express.urlencoded({extended: false}))
app.use(express.json())

app.use('/', router) // write all your routes in this file 'router'

module.exports = app

You need to render the HTML file in your server on port ‘3000’. I think you are trying to access ‘http://localhost:3000/registerauth‘ directly while rendering the html page outside the server.

Make these changes to App.js file

const express = require('express');
const app= express();
const path = require('path');
const port = process.env.PORT || 3000;
const login = require('./routes/login'); /*MODULE THAT HAS THE CONTROLLER CODE*/

app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(express.static(path.join(__dirname, 'public')));

//newly added code
app.get('/',(req,res)=>{
    res.sendFile('index.html');

})

app.post('/registerauth',function (req,res,next){  /*TRIED THIS BUT DIDN'T WORK*/
    console.log("testing");
    res.json(req.body);
    // Redirect to '/login' here instead of sending response which will trigger the login module
})

app.use('/login', login); /*TRIED CALLING THE MODULE THAT HAS THE CONTROLLER AND DELETING THE LINE ABOVE BUT DIDN'T WORK*/

app.listen(port, ()=> console.log(`server started on port ${port} `))

Render the html page when you hit ‘http://localhost:3000‘. Also, inorder for your login component to work you need to redirect to ‘/login/’ path in the POST request

I am new learning NodeJS + Express and now I am trying to build a simple register form but I keep getting the same error with this and other forms:

Cannot POST /registerauth

I have looked through dozens of similiar questions in stackoverflow and other sites but I have not found an answer that applies for my case.

Here is the form:

<form id="register-form" class="panel-form" action="/registerauth" method="POST">
          <input type="text" name="register-username" id="register-username" class="fill-input" placeholder="Username *" autofocus="true" maxlength="15" required>

          <input type="password" name="register-password" id="register-password" class="fill-input" placeholder="Password *" maxlength="30" required>


                        <button type="submit">Register</button>
                    </form>

My app.js file:

const express = require('express');
const app= express();
const path = require('path');
const port = process.env.PORT || 3000;
const login = require('./routes/login'); /*MODULE THAT HAS THE CONTROLLER CODE*/

app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(express.static(path.join(__dirname , 'public')));

app.post('/registerauth',function (req,res,next){  /*TRIED THIS BUT DIDN'T WORK*/
    console.log("testing");
    res.json(req.body);
})

app.use('/login', login); /*TRIED CALLING THE MODULE THAT HAS THE CONTROLLER AND DELETING THE LINE ABOVE BUT DIDN'T WORK*/

app.listen(port, ()=> console.log(`server started on port ${port} `))

The module that has the controller code but it’s not even called :

const express    = require('express');
const oracledb    = require('oracledb');
const router        = express.Router();
const dbConfig =require('../dbconfig.js') ;

class Cliente{
    constructor(username,password,nombre,email){
        this.username = username;
        this.password=password;
        this.nombre=nombre;
        this.email=email;
    }
}

    let conexion;

    router.post('/registerauth',async(req,res,next)=>{ /*all this is not working neither*/

        try{
            console.log("THIS IS NOT WORKING");

            cliente = new Cliente(req.body.username, req.body.password,req.body.nombre,req.body.email);

     conexion= await oracledb.getConnection(dbConfig);
     const result = await conexion.execute(
        `INSERT INTO Cliente values (${cliente.username}, ${cliente.password},
 ${cliente.nombre}, ${cliente.email})`
     );
} catch(err){
    console.error(err);
}finally{
    conexion.close();
}
    })

module.exports = router;

And I have my project folder structured this way:

/
 node_modules
 public/
       css/
       media/
       scripts/
       index.html (just the file inside public folder)
       register.html (just the file inside public folder THIS IS THE REGISTER FORM FILE)
 routes/
       api/
          login.js
 app.js
 dbconfig.js
 package-lock.json
 package.json

Note: I created other forms in my project with different action methods and all of them gave the same error