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Client on Node.js: Uncaught ReferenceError: require is not defined
(11 answers)
Closed 5 months ago.
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.
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.
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.
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
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.
Just remove "type":"module" from your package.json.
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.
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".
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
I solve it, by removing below line from package.json file
"type": "module"
Hope it will solve the problem.
Related
In my electron app I have a python file that has two import statements shown below
import requests
import shutil
The app works fine without an errors in the IDE but after packaging the electron app with
npx electron-packager ./ --platform=darwin --icon=src/img/logo.icns
The app gives me this error
It only gives this error for the 'requests' module but not the 'shutil' module. And yes, 'requests' is installed on my computer. I also use the PythonShell module in the js file to run the python file like below
function version_checker(){
form.classList.toggle('hide');
circle.classList.toggle('show');
let pyshell = new PythonShell(__dirname + '/version_checker.py');
pyshell.on('message', function (message){
console.log(message);
if(message !== "same"){
console.log("updating")
}
else{
if(message !== "restart"){
form.classList.toggle('hide');
circle.classList.toggle('show');
}
else{}
}
})
pyshell.end(function (err,code,signal) {
if (err) throw err;
console.log('The exit code was: ' + code);
console.log('The exit signal was: ' + signal);
console.log('finished');
});
}
I also do not wish to compile the python file into an executable because the python script "talks" to the js file. I am also on a M1 Pro Macbook running macOS Ventrua if that helps
How do I package the app and include the 'requests' module OR How do I make the 'requests' module work with the packaged app
I did find a stackoverflow post that asked a similar question but the owner voluntary took down the question so I wasn't able to view it
I looked at this post but it wasn't helpful because I'm not using 'anaconda' or 'child-process'
PythonShell just calls the system's Python interpreter, so use PIP to install the requests library
Or specify the interpreter as follows:
new PythonShell(__dirname + '/version_checker.py', {
pythonPath: '/path/to/python'
})
Note: For production purposes, it is recommended to include an interpreter in electron and install dependencies
It seems you just want to make a HTTP request, why not try fetch in javascript?
If the error is ModuleNotFoundError, then your python interpreter is struggling to find the requests module. This can happen for a number of reasons:
Module does not exist: We can rule this out if your ide ran program successfully.
2: Module is not where interpreter expects to find it: Most likely.
Almost certainly the python interpreter used by your IDE is different to the one you ran after packaging the electron app.
The solution is to either:
a. make sure the location of requests is visible to the PYTHONPATH by setting that in the proper location (I don't use MAC but I believe you have ~/.bash_profile file to set it in or
b. Explicitly add the request module location via a sys.path.append command in your code eg
import sys
import os
path = 'your path to request module'
sys.path.append(os.path.join(path, 'requests')
import requests
You should be able to find the path location by investigating your IDE and looking where you set the module to be included in your program
When I import node:process it works fine. However, when I try to require the same, it gives an error.
This works fine:
import process from 'node:process';
But when I try to require the same, it throws an error:
const process = require('node:process');
Error: Cannot find module 'node:process'
I am curious as to what is the difference between process, which works in both, commonjs and module, vs node:process.
Also, a follow-up, I am using webpack to bundle my js, and I discovered this error when I tried to run my bundled code and realised, that chalk imports node:process, node:os and node:tty. How do I solve that now?
import process from 'node:process'; and import process from 'process'; are equivalent.
The node: exists since version 12 for import.
node: URLs are supported as an alternative means to load Node.js builtin modules. This URL scheme allows for builtin modules to be referenced by valid absolute URL strings.
The idea behind node: is to make clear that it is actually a buildin module and not one installed and to avoid name conflicts, with 3rd party modules.
The node: protocol was first added only for import so a particular node version might support node: with import but not with require.
In v16.13.0 (not sure since which v16 version) you can also use it with require. And was also backported to v14 since v14.18: module: add support for node:‑prefixed require(…) calls
"node:" is an URL scheme for loading ECMAScript modules. As such it started for "import", not "require".
"node:process" is just an alternative name to load the built-in "process" module.
See also Node.js documentation - you can find the lowest supporting Node.js version inside the "History" tag (12.20.0, 14.13.1)
With newer Node.js it should be available for "require" as well (14.18.0, 16.0.0).
Some more details can be found here: node:process always prefers the built-in core module, while process could be loaded from a file.
This has been asked a million times and answered a million times. But i still can't find a solution. The code im using is exactly the one in the Library docs usage examples:
import WebSocket from 'ws';
const ws = new WebSocket('ws://www.host.com/path');
ws.on('open', function open() {
ws.send('something');
});
ws.on('message', function message(data) {
console.log('received: %s', data);
});
I haven't changed one single line of code and this is the only code i have in Node Js. But my result is the error : "Warning: to load an es module set type module in the package.json or use the .mjs extension" no matter what.
I know the answer is simply to change the "type" to "module" in "package.json" file, i have read this a thousand times. The only problems is: I have like a million package.json files in my NodeJS folder and i have no idea which one i should update. Can someone please help?
I have no experience in NodeJS or WS Library,so any hint or any other solution to my problem is welcome.
As the error message suggested, if you want to use ECMAScript modules in a Node.js application you can either:
Change the file extension to .mjs
Add "type": "module" entry at the top level to the nearest package.json
At this time Node.js will treat all other forms of input as CommonJS modules (where you use require to import).
Note
This may change in the future, and ECMAScript modules might become the default, so it is recommended to be always explicit, and if you want to use CommonJS, use .cjs extension or add "type": "commonjs" to the (nearest) package.json file.
So I'm planning on writing a package which a user will hopefully be able to use on both Node.js and in the browser.
On the Node.js side it will use the fs module. This does not exist in the browser perhaps. This could be accomplished with CommonJS with an if clause to check which environment the module is in and a simple require.
This is not the case with import as it is hoisted.
Does anyone have an idea of how to structure the code or the build environment to satisfy both enviroments in the same package?
Stick to ES6 imports
It seems there was an improvement in import support in Node.js. In the docs it says:
The --experimental-modules flag can be used to enable support for
ECMAScript modules (ES modules).
Once enabled, Node.js will treat the following as ES modules when
passed to node as the initial input, or when referenced by import
statements within ES module code:
Files ending in .mjs.
Files ending in .js, or extensionless files, when the nearest parent package.json file contains a top-level field "type" with a
value of "module".
Strings passed in as an argument to --eval or --print, or piped to node via STDIN, with the flag --input-type=module.
The second listed approach may be useable with node.js. Simply make sure your librarie's package.json contains "type": "module" and Node should treat it as a ES6 module instead of CommonJS.
Conditional import as promise - you will have to wait
Conditional imports are already available in node but not actually supported. They seem to work in browser. And there's a caveat: the imported module is a promise. What that means is that you can have partially isomorphic code as long as you plan your steps well. Knowing that you can do import("test.js") in browser and that you can test for window means you can write conditions in a smart way and have cross-platform code.
For example you can do:
if (typeof window !== 'undefined') const FooPromise = import("foo");
But not the opposite. Good luck. Hopefully more support for the es6 dynamic import will come to node.
I have a scenario where I want to export data to CSV from the client-side. I will have a textbox/area or whatever where the user can input data and then ideally with one click, a local CSV file will be updated with that data.
This is easily achievable with NodeJS with server interaction, and its core modules (specifically fs module), but apparently not so much from a browser.
I found out that certain node modules (for example underscore), support RequireJS's method of making a particular module work in the browser. So for underscore I did this:
methods.js
define(['underscore'],function(_) {
var Methods = {
doSomething: function() {
var x = _.size({one: 1, two: 2, three: 3, xuz: 3});
alert(x);
}
};
return Methods;
});
common.js
requirejs.config({
baseURL: 'node_modules',
paths: {
underscore: 'underscore/underscore',
}
});
require(['methods'], function(y){
y.doSomething();
});
index.html
<script data-main="common" src="require.js"></script>
<script>
require(['common'], function() {
require(['methods.js']);
});
</script>
The above works fine and will show an alert: 4.
But when I try the same with the fs module it won't work. It will show this error:
Module name "util" has not been loaded yet for context: _. Use require([])
As far as I can understand, this is because fs requires several other modules, one of them being util.
So I proceeded to add all these modules to the RequireJS config. But still no luck, so I specifically tested util module by itself as this doesn't seem to require other modules to work.
And now I am stuck on this error: Uncaught ReferenceError: exports is not defined
I tried modularizing this util module by encapsulating the whole module source code in this:
define([], function() {})
But it didn't work either... I've also tried copying underscore's model but still no luck.
So I was wondering if anyone managed to use util & fs modules (or any other core NodeJS modules) within the browser with libraries such as RequireJS or Browserify.
That's right, exports is node-specific JS (used to make part of your module available outside the module) and isn't supported by web-browsers. Even though NodeJS is technically JS, there are client specific properties (like the window property for browsers, and exports for NodeJS apps) that can't be interchanged.
That said, here's a client side JS answer to the CSV problem.
Your best bet (and probably only one) is to use HTML5 FileSystem API. I am not aware of any other browser feature that would allow to work with files on client computer except maybe Flash and similar solution.
I am bit confused by your browserify tag since you are not obviously using Browserify. That would fix your issue with "exports is not defined".