Intro
I had made a Login form.
I had deployed the frontend on Netlify here and the backend on Heroku here. This is my backend logs https://dashboard.heroku.com/apps/my-notebook-mohit/logs
My index.js is
const connectToMongo = require('./db');
const express = require('express');
connectToMongo();
var cors = require('cors')
const app = express()
const port = 5000
//to use req body 
app.use(cors())
app.use(express.json())
//Available routes
app.use('/api/auth',require('./routes/auth'));
app.use('/api/notes',require('./routes/notes'));
app.listen(process.env.PORT || port , () => {
  console.log(`my-notebook backend listening at http://localhost:${process.env.PORT || port}`)
})
LoginPage.js
import React, { useState } from "react";
import { useHistory } from "react-router-dom";
import imgpath from "../assets/notepic.jpg";
import { motion } from "framer-motion";
const Login = (props) => {
  let history = useHistory();
  const [credentials, setCredentials] = useState({ email: "", password: "" });
  const onChange = (e) => {
    setCredentials({ ...credentials, [e.target.name]: e.target.value });
    //input mei value typed ho sake,jaise jaise value change ho vese-vese note me set ho jaye
  };
  const goToSignup = () => {
    history.push("/signup");
  };
  
  const handleSubmit = async (e) => {
    e.preventDefault();
    const response = await fetch("http://localhost:5000/api/auth/login", {
      method: "POST",
      headers: {
        "Content-Type": "application/json",
      },
      body: JSON.stringify({
        email: credentials.email,
        password: credentials.password,
      }),
    });
    const json = await response.json();
    if (json.success === true) {
      //storing the authtoken
      localStorage.setItem("token", json.authToken);
      props.showAlert("User logged in successfully", "info");
      history.push("/");
    } else {
      props.showAlert("invalid Credentials", "danger");
    }
    console.log(json);
  };
  return (
   .....
   <form onSubmit={handleSubmit} className="login-form">
           .....
           ....
   </form>
  ...
  ...
};
export default Login;
Problem I facing
When I make a POST request on the login button from frontend deployed on Netlify, it goes to http://localhost:5000/api/auth/login as it makes the fetch request there only , hence shows error.
What I think?
The reason I could think is that Heroku is dynamically assigning the any other port i.e. 49004 when I check from Heroku Logs and my request is sent over port 5000.
How do I add the dynamic port to the fetch request I made?
