TypeError: Cannot read properties of undefined (reading 'prototype') React Typescript + Express

Question

I'm trying to use express at my React-Typescript SPA. But It's giving me the error:

    TypeError: Cannot read properties of undefined (reading 'prototype')
(anonymous function)
node_modules/express/lib/response.js:42
  39 |  * @public
  40 |  */
  41 | 
> 42 | var res = Object.create(http.ServerResponse.prototype)
  43 | 
  44 | /**
  45 |  * Module exports.

I've tried adding target: "node" to my "node_modules/react-scripts/config/webpack.config.js" But it won't work...

Here's some ways I've already tried to solve it:

    import express from "express";
    app = express();
---------------
    import express from "express";
    let app: express.Application;
    app = express();
-------------

    import express from "express";
    let app: any;
    app = express();

-------------
    const express require("express");
    let app: express.Application;
    app = express();

I think the problem is you forgot to instantiate app with const, var, or let for the first example, since it should work. — Kenneth Lew
– Kenneth Lew, Commented Sep 2, 2021 at 1:57
@KennethLew sorry I copied incorrectly, but my I was using const app = express() — rafaelpadu
– rafaelpadu, Commented Sep 2, 2021 at 2:22

santas_little_helper · Accepted Answer · 2021-09-22 10:24:00Z

9

You have to instantiate both the app and express, use the const keyword as well.

const express = require('express');
const app = express();

Also, look for anywhere in your code base where you have:

import { response } from 'express';

Often this is put in by mistake and removing this line may solve the error

answered Sep 22, 2021 at 10:24

santas_little_helper

911 bronze badge

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1 Comment

Vitaly Dubyna Over a year ago

Thanks a lot. It was this thing: "import { response } from 'express". Spent an hour looking for the problem, you saved me a log of time)

valentin_nm · Accepted Answer · 2021-11-19 00:13:33Z

3

Faced same issue

it was imported under

import e from "express";

not sure cuz of any random IntelliSense extension or maybe the GH copilot auto-completion

answered Nov 19, 2021 at 0:13

valentin_nm

413 bronze badges

1 Comment

Keaton Benning Over a year ago

YES my VSCode added that line to the top of my file randomly.... thank you !

Nilabja Sarkar · Accepted Answer · 2023-07-27 06:47:21Z

1

faced the same issue

var res = Object.create(http.ServerResponse.prototype)

change it to

let res = Object.create(http.ServerResponse.prototype)

answered Jul 27, 2023 at 6:47

Nilabja Sarkar

11 bronze badge

1 Comment

Quack E. Duck Over a year ago

That's interesting, I wonder why changing from function scoped to block scoped fixes the problem?

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