require is not defined? Node.js

Question

Just started working with Node.js. In my app/js file, I am doing something like this:

app.js

var http = require('http');

http.createServer(function (request, response) {
  response.writeHead(200, {'Content-Type': 'text/plain'});
  response.end('Am I really running a server?!');
}).listen(8080, '127.0.0.1');

console.log('running server!');

When I'm in my terminal and run node app.js, the console spits out 'running server!', but in my browser I get, Uncaught ReferenceError: require is not defined.

Can someone explain to me why in the terminal, it works correctly but in the browser, it doesn't?

I am using the node's http-server to serve my page.

Answer 1

This can now also happen in Node.js as of version 14.

It happens when you declare your package type as module in your package.json. If you do this, certain CommonJS variables can't be used, including require.

To fix this, remove "type": "module" from your package.json and make sure you don't have any files ending with .mjs.

Answer 2

In the terminal, you are running the node application and it is running your script. That is a very different execution environment than directly running your script in the browser. While the Javascript language is largely the same (both V8 if you're running the Chrome browser), the rest of the execution environment such as libraries available are not the same.

node.js is a server-side Javascript execution environment that combines the V8 Javascript engine with a bunch of server-side libraries. require() is one such feature that node.js adds to the environment. So, when you run node in the terminal, you are running an environment that contains require().

require() is not a feature that is built into the browser. That is a specific feature of node.js, not of a browser. So, when you try to have the browser run your script, it does not have require().

There are ways to run some forms of node.js code in a browser (but not all). For example, you can get browser substitutes for require() that work similarly (though not identically).

But, you won't be running a web server in your browser as that is not something the browser has the capability to do.

---

You may be interested in browserify which lets you use node-style modules in a browser using require() statements.

Answer 3

As Abel said, ES Modules in Node >= 14 no longer have require by default.

If you want to add it, put this code at the top of your file:

import { createRequire } from 'module';
const require = createRequire(import.meta.url);

Source: https://nodejs.org/api/modules.html#modules_module_createrequire_filename

Answer 4

Node.JS is a server-side technology, not a browser technology. Thus, Node-specific calls, like require(), do not work in the browser.

See browserify or webpack if you wish to serve browser-specific modules from Node.

Answer 5

Just remove "type":"module" from your package.json.

Answer 6

I solve this by doing this steps:-

step 1: create addRequire.js file at the project root.

step 2: inside addRequire.js add this lines of code

import { createRequire } from "module";
const require = createRequire(import.meta.url);

global.require = require; //this will make require at the global scobe and treat it like the original require

step 3: I imported the file at the app.js file head

import "./start/addRequire.js";

now you have require beside import across the whole project and you can use both anywhere.

Answer 7

Point 1: Add require() function calling line of code only in the app.js file or main.js file.

Point 2: Make sure the required package is installed by checking the pacakage.json file. If not updated, run "npm i".

Answer 8

My mistake: I installed ESLint to my project and made a mistake when I filled out the questionnaire and chose wrong type of modules) Maybe it will be helpful for someone))

What type of modules does your project use? · * commonjs

Answer 9

I solve it, by removing below line from package.json file

 "type": "module"

Hope it will solve the problem.