Express Middleware not rendering the view - node.js

Question

I have written an auth middleware , which when fails , I want to render a page instead of sending response to my xhr request . How to do it ?
const jwt = require('jsonwebtoken')
const User = require('../models/users')
const express = require('express')
const auth = async (req, res ,next) => {
try {
//res.render("404")
const token = req.header('Authorization').replace('Bearer ' , '') //token comes from client in the header section named Auth(here)
const data = jwt.verify(token , 'itistechvaulttoken') //this gives back the id of the user and also iat :- issued at , a callback can be attached to
// .verify :-- see jsonwebtoken documentation for details .
const user = await User.findOne({ _id : data._id})
if(!user) {
throw new Error()
}
req.token = token //this is being use mainly for logout route handler
req.user = user
next()
} catch(e) {
res.status(401).render("404")
}
}
module.exports = auth
I have create a form and sending that data to my backend using xhr request to route and from there i am redirecting it to another route where I want to render the view .
My routes :-
router.post('/users' ,async (req, res) => {
console.log("Request Recieved")
const user = new User(req.body)
try {
await user.save()
const token = await user.generateAuthToken()
//console.log(token)
//res.status(201).send({ user , token})
req.accesstoken = token
res.redirect(302 , "/users/me" )
}
catch(e) {
console.log(e)
res.status(400).send("User not created" + e)
}
})
/user/me :-
router.get('/users/me', auth, async (req, res) => {
console.log("in users/me")
res.send(req.user)
})
I know here authentication has to fail, and code under the catch of middleware should run ,where I am trying to render a view but failing .

Answer 1

I guess you want your xhr endpoint code on your server to make your user's browser display an error page of some kind upon auth failure.
To do that you need the Javascript code in your browser to detect an error message in the response to the xhr request and navigate to the error page. Your nodejs app can't force any kind of redirect when responding to an xhr request without cooperation from the browser.