Client on Node.js: Uncaught ReferenceError: require is not defined

I am writing an application with the Node.js, Express.js, and Jade combination.

I have file client.js, which is loaded on the client. In that file I have code that calls functions from other JavaScript files. My attempt was to use

var m = require('./messages');

in order to load the contents of messages.js (just like I do on the server side) and later on call functions from that file. However, require is not defined on the client side, and it throws an error of the form Uncaught ReferenceError: require is not defined.

These other JavaScript files are also loaded at runtime at the client, because I place the links at the header of the webpage. So the client knows all the functions that are exported from these other files.

How do I call these functions from these other JavaScript files (such as messages.js) in the main client.js file that opens the socket to the server?

This is because require() does not exist in the browser/client-side JavaScript.

Now you're going to have to make some choices about your client-side JavaScript script management.

You have three options:

1. Use the <script> tag.
2. Use a CommonJS implementation. It has synchronous dependencies like Node.js
3. Use an asynchronous module definition (AMD) implementation.

CommonJS client side-implementations include (most of them require a build step before you deploy):

1. Browserify - You can use most Node.js modules in the browser. This is my personal favorite.
2. Webpack - Does everything (bundles JavaScript code, CSS, etc.). It was made popular by the surge of React, but it is notorious for its difficult learning curve.
3. Rollup - a new contender. It leverages ES6 modules and includes tree-shaking abilities (removes unused code).

You can read more about my comparison of Browserify vs (deprecated) Component.

AMD implementations include:

1. RequireJS - Very popular amongst client-side JavaScript developers. It is not my taste because of its asynchronous nature.

Note, in your search for choosing which one to go with, you'll read about Bower. Bower is only for package dependencies and is unopinionated on module definitions like CommonJS and AMD.

I am coming from an Electron environment, where I need IPC communication between a renderer process and the main process. The renderer process sits in an HTML file between script tags and generates the same error.

The line

const {ipcRenderer} = require('electron')

throws the Uncaught ReferenceError: require is not defined

I was able to work around that by specifying Node.js integration as true when the browser window (where this HTML file is embedded) was originally created in the main process.

function createAddItemWindow() {

    // Create a new window
    addItemWindown = new BrowserWindow({
        width: 300,
        height: 200,
        title: 'Add Item',

        // The lines below solved the issue
        webPreferences: {
            nodeIntegration: true,
            contextIsolation: false
        }
})}

That solved the issue for me. The solution was proposed here.

ES6: In HTML, include the main JavaScript file using attribute type="module" (browser support):

<script type="module" src="script.js"></script>

And in the script.js file, include another file like this:

import { hello } from './module.js';
...
// alert(hello());

Inside the included file (module.js), you must export the function/class that you will import:

export function hello() {
    return "Hello World";
}

A working example is here. More information is here.

Replace all require statements with import statements. Example:

// Before:
const Web3 = require('web3');

// After:
import Web3 from 'web3';

It worked for me.

This worked for me

1. Get the latest release from the RequireJS download page
   It is the file for RequestJS which is what we will use.
2. Load it into your HTML content like this: <script data-main="your-script.js" src="require.js"></script>
   

Notes!

Use require(['moudle-name']) in your-script.js, not require('moudle-name')

Use const {ipcRenderer} = require(['electron']), not const {ipcRenderer} = require('electron')

In my case I used another solution.

As the project doesn't require CommonJS and it must have ES3 compatibility (modules not supported) all you need is just remove all export and import statements from your code, because your tsconfig doesn't contain

"module": "commonjs"

But use import and export statements in your referenced files

import { Utils } from "./utils"
export interface Actions {}

Final generated code will always have(at least for TypeScript 3.0) such lines

"use strict";
exports.__esModule = true;
var utils_1 = require("./utils");
....
utils_1.Utils.doSomething();

Even using this won't work. I think the best solution is Browserify:

module.exports = {
  func1: function () {
   console.log("I am function 1");
  },
  func2: function () {
    console.log("I am function 2");
  }
};

-getFunc1.js-
var common = require('./common');
common.func1();

window = new BrowserWindow({
    webPreferences: {
        nodeIntegration: true,
        contextIsolation: false
    }
});

I confirm. We must add:

webPreferences: {
    nodeIntegration: true
}

For example:

mainWindow = new BrowserWindow({webPreferences: {
    nodeIntegration: true
}});

For me, the problem has been resolved with that.

People are asking what is the script tag method. Here it is:

<script src='./local.js'></script>. 

Or from network:

<script src='https://mycdn.com/myscript.js'></script>

You need plugin the right url for your script.

I was trying to build metronic using webpack. In my package.json I had to remove the "type": "module" section.