I would like to send 'cookieValue' to my backend but I'm not quite sure how to and haven't been able to find any good resources online.

Currently, I don't believe that my 'cookieValue' actually has a value when I try to send it to my backend. I am also getting a waring saying that 'cookieValue' is declared but never used in my 'findCookie function'. Below I have my current code, any help would be appreciated.

Front End Code:

import axios from 'axios'
import { Outlet, Navigate } from "react-router";
import { useState } from 'react'

let backEndResponse = null


function SendCookie() {
    
    const [cookieValue, setCookieValue] = useState("");

    if (document.cookie != null) {
           const cookieValue = document.cookie
                .split('; ')
                .find(row => row.startsWith('Auth='))
                .split('=')[1];
    
        axios.post('http://localhost:5000/auth', {
            cookieValue,

        }).then(getBackEndResponse => {
            return axios.get('http://localhost:5000/auth', { withCredentials: true }).then((res) => {
                res.render(backEndResponse);
            })
        });

    } else {

    }
}



const useAuth = () => {
    if (backEndResponse) {
        const authorized = {loggedIn: true}
        return authorized && authorized.loggedIn;
    } else {
        const authorized = {loggedIn: false}
        return authorized && authorized.loggedIn;
    }
};

const ProtectedRoutes = () => {
    const isAuth = useAuth();
    return isAuth ? <Outlet/> : <Navigate to="/login" />;
}

export default ProtectedRoutes

Backend Code:

app.post('/auth', (req, res) => {
    const authCookie = req.body.cookieValue

    if (authCookie === result) {
        backEndResponse = true
    } else {
        backEndResponse = false
    }
});

app.get('/auth', (req, res) => {
    res.render(backEndResponse)
});