In NodeJS I have:
const fs = require('fs');
if (!fs.existsSync("some_path")) {
...
}
But I get the error:
TypeError: fs.existsSync is not a function
After doing some searching, I read that Webpack brings its own require which clobbers node.js's require, so when you require a node.js core module that webpack can't resolve to one of your files or dependencies, it throws.
(My stack trace includes __webpack_require__)
But how can I fix it?
I was facing the same Error like TypeError: fs.existsSync is not a function
So, I figured out that one extra line was added automatically which was creating this issue in import.
after removing this line from import
import { TRUE } from "node-sass";
the issue has been resolved.
I had the same error that you have. Your vscode might have added a new module to your js file. Remove that module and your app should work just fine.
You can allow webpack to use the Node's require and include fs etc. by targeting node in the config:
module.exports = {
entry: './src/main.js',
target: 'node',
output: {
path: path.join(__dirname, 'build'),
filename: 'backend.js'
}
}
As described here: https://webpack.js.org/concepts/targets/ and https://webpack.js.org/configuration/target/
I was working on an electron application, I wanted to send a message from node and get in on the react side, but I was having that same issue when requiring ipcRenderer from electron, I tried
import { ipcRenderer } from 'electron';
and
const { ipceRenderer } = require('electron') This leads to an error due to webpack transforming node's require to its own webpack_require. See more info here
What worked for me was to use
const {ipcRenderer} = window.require('electron'); on the react side/renderer side from electron
In my case, I forgot that I'd only imported the promises API, const fs = require("fs").promises, which doesn't have exist or existsSync functions in Node 17.4.0.
To use exist or existsSync, make sure you've imported fs using the sync API (const fs = require("fs")).
Note: I'm adding this answer as a possible solution for future visitors to a canonical thread for the error, not OP who appears to have required fs correctly.
It is nothing to worry about, check your code for something like import { types } from "node-sass";, it would have mistakenly and automatically imported without you know. Remove that line, and everything should work perfectly.
Even if it is not type, it is something from node-sass in your node_modules file, and you can't edit that file.
So look for and remove import { types } from "node-sass"
In my case VSCode added a arbitrary import from electron. After removing it my application worked.
import { Menu } from 'electron';
In my case, i needed to send a message from the node to react. I tried importing ipcRenderer from 'electron'; and const ipceRenderer = require('electron') This results in an error owing to webpack changing the node's require to its own webpack require. See more info here
Related
I was checking the node official docs and I found that the import url of the node native modules in the examples of es modules starts with node:.
I did not use node very much, maybe there were some huge changes happened. So:
Can someone share some links that I can get some context about this change?
What if we don't add the node: before the import url? I tested a bit and it seems everythings works fine.
Thanks a lot.
import { open } from 'node:fs/promises';
let filehandle;
try {
filehandle = await open('thefile.txt', 'r');
} finally {
await filehandle?.close();
}
I wrote some node packages and use "type": "module" in pacakge.json and not use node: when I import native modules, I did not see any errors.
From the docs:
Core modules can be identified using the node: prefix, in which case it bypasses the require cache. For instance, require('node:http') will always return the built in HTTP module, even if there is require.cache entry by that name.
good guys I'm still learning and since I'm facing this type of error, I don't know what to do for the code to accept calling as index.js, should I be worried about that? all files i have to change the file to "index.mjs" to work correctly. what I would like to know is if I should accept this or do I have to fix it to run as index.js could you tell me if there is a problem with everything being in mjs?
const inquirer = require('inquirer')
const chalk = require('chalk')
inquirer.prompt([
{name: "p1", message: `${chalk.green("what is your first name: ")}`},
{name: "p2", message: `${chalk.green("what is years old: ")}`}
])
.then((answers) => {
console.log(`${chalk.yellow(answers.p1, answers.p2)}`)
const infoName = answers.p1
const infoAge = answers.p2
console.log(`his name is ${chalk.red(infoName)} and your age is ${chalk.red(infoAge)} years old`)
}).catch((err) => {
console.log(err)
})
this is the error that appears when I try to run with the index.js file
Error [ERR_REQUIRE_ESM]: require() of ES Module C:\Users\Odin\OneDrive\Área de Trabalho\nodejs tarefas\Fundamentos\node_modules\inquirer\lib\inquirer.js from C:\Users\Odin\OneDrive\Área de Trabalho\nodejs tarefas\Fundamentos\index.js not supported.
Instead change the require of inquirer.js in C:\Users\Odin\OneDrive\Área de Trabalho\nodejs tarefas\Fundamentos\index.js to a dynamic import() which is available in all CommonJS modules.
at Object.<anonymous> (C:\Users\Odin\OneDrive\Área de Trabalho\nodejs tarefas\Fundamentos\index.js:1:18) {
code: 'ERR_REQUIRE_ESM'
}
Node.js v18.13.0
baixei a versão mais recente,
The reason for this is that inquirer is a pure-ESM package.
What is ESM?
Node.js appeared long before import/export support in JS. So it's used (and still is) so called require.js for imports.
Later, Node.js added support for ES modules, but with some limitations. One of these limitations is that ESM script can only be imported from another ESM script.
What to do?
The Node.js ecosystem is slowly migrating to the ESM. So you can continue using ESM, but you should avoid using require and use import instead. E.g.:
import inquirer from 'inquirer';
If you want to use require, you have to downgrade inquirer to version 8+
You can also use TypeScript with esModuleInterop and always use import/export.
I initiated a basic ReactJS app using npx create-react-app, then I ejected using npm run eject. Now when I am trying to import the Casual library by import casual from 'casual';, I get the following error:
Compiled with problems:
ERROR in ./node_modules/casual/src/casual.js 3:13-37
Module not found: Error: Can't resolve 'fs'
in '/home/me/project/node_modules/casual/src'
And the code around line number 3 in casual.js looks like this:
var helpers = require('./helpers');
var exists = require('fs').existsSync;
var safe_require = function(filename) {
if (exists(filename + '.js')) {
return require(filename);
}
return {};
};
...
I found answers to similar questions. Those were mainly Node or Angular related. I also tried answers suggesting some changes in webpack config, but no luck.
The reason is Casual doesn't work on the front end. It runs on Node.js only.
You need to install maybe a new package to make things work.
Fs is unavailable on the browser so it won't work. Instead, you should use casual-browserify, it will work on browsers.
I try to import a node module inside an Angular 8 web worker, but get an compile error 'Cannot find module'. Anyone know how to solve this?
I created a new worker inside my electron project with ng generate web-worker app, like described in the above mentioned ng documentation.
All works fine until i add some import like path or fs-extra e.g.:
/// <reference lib="webworker" />
import * as path from 'path';
addEventListener('message', ({ data }) => {
console.log(path.resolve('/'))
const response = `worker response to ${data}`;
postMessage(response);
});
This import works fine in any other ts component but inside the web worker i get a compile error with this message e.g.
Error: app/app.worker.ts:3:23 - error TS2307: Cannot find module 'path'.
How can i fix this? Maybe i need some additional parameter in the generated tsconfig.worker.json?
To reproduce the error, run:
$ git clone https://github.com/hoefling/stackoverflow-57774039
$ cd stackoverflow-57774039
$ yarn build
Or check out the project's build log on Travis.
Note:
1) I only found this as a similar problem, but the answer handles only custom modules.
2) I tested the same import with a minimal electron seed which uses web workers and it worked, but this example uses plain java script without angular.
1. TypeScript error
As you've noticed the first error is a TypeScript error. Looking at the tsconfig.worker.json I've found that it sets types to an empty array:
{
"compilerOptions": {
"types": [],
// ...
}
// ...
}
Specifying types turns off the automatic inclusion of #types packages. Which is a problem in this case because path has its type definitions in #types/node.
So let's fix that by explicitly adding node to the types array:
{
"compilerOptions": {
"types": [
"node"
],
// ...
}
// ...
}
This fixes the TypeScript error, however trying to build again we're greeted with a very similar error. This time from Webpack directly.
2. Webpack error
ERROR in ./src/app/app.worker.ts (./node_modules/worker-plugin/dist/loader.js!./src/app/app.worker.ts)
Module build failed (from ./node_modules/worker-plugin/dist/loader.js):
ModuleNotFoundError: Module not found: Error: Can't resolve 'path' in './src/app'
To figure this one out we need to dig quite a lot deeper...
Why it works everywhere else
First it's important to understand why importing path works in all the other modules. Webpack has the concept of targets (web, node, etc). Webpack uses this target to decide which default options and plugins to use.
Ordinarily the target of a Angular application using #angular-devkit/build-angular:browser would be web. However in your case, the postinstall:electron script actually patches node_modules to change that:
postinstall.js (parts omitted for brevity)
const f_angular = 'node_modules/#angular-devkit/build-angular/src/angular-cli-files/models/webpack-configs/browser.js';
fs.readFile(f_angular, 'utf8', function (err, data) {
var result = data.replace(/target: "electron-renderer",/g, '');
var result = result.replace(/target: "web",/g, '');
var result = result.replace(/return \{/g, 'return {target: "electron-renderer",');
fs.writeFile(f_angular, result, 'utf8');
});
The target electron-renderer is treated by Webpack similarily to node. Especially interesting for us: It adds the NodeTargetPlugin by default.
What does that plugin do, you wonder? It adds all known built in Node.js modules as externals. When building the application, Webpack will not attempt to bundle externals. Instead they are resolved using require at runtime. This is what makes importing path work, even though it's not installed as a module known to Webpack.
Why it doesn't work for the worker
The worker is compiled separately using the WorkerPlugin. In their documentation they state:
By default, WorkerPlugin doesn't run any of your configured Webpack plugins when bundling worker code - this avoids running things like html-webpack-plugin twice. For cases where it's necessary to apply a plugin to Worker code, use the plugins option.
Looking at the usage of WorkerPlugin deep within #angular-devkit we see the following:
#angular-devkit/src/angular-cli-files/models/webpack-configs/worker.js (simplified)
new WorkerPlugin({
globalObject: false,
plugins: [
getTypescriptWorkerPlugin(wco, workerTsConfigPath)
],
})
As we can see it uses the plugins option, but only for a single plugin which is responsible for the TypeScript compilation. This way the default plugins, configured by Webpack, including NodeTargetPlugin get lost and are not used for the worker.
Solution
To fix this we have to modify the Webpack config. And to do that we'll use #angular-builders/custom-webpack. Go ahead and install that package.
Next, open angular.json and update projects > angular-electron > architect > build:
"build": {
"builder": "#angular-builders/custom-webpack:browser",
"options": {
"customWebpackConfig": {
"path": "./extra-webpack.config.js"
}
// existing options
}
}
Repeat the same for serve.
Now, create extra-webpack.config.js in the same directory as angular.json:
const WorkerPlugin = require('worker-plugin');
const NodeTargetPlugin = require('webpack/lib/node/NodeTargetPlugin');
module.exports = (config, options) => {
let workerPlugin = config.plugins.find(p => p instanceof WorkerPlugin);
if (workerPlugin) {
workerPlugin.options.plugins.push(new NodeTargetPlugin());
}
return config;
};
The file exports a function which will be called by #angular-builders/custom-webpack with the existing Webpack config object. We can then search all plugins for an instance of the WorkerPlugin and patch its options adding the NodeTargetPlugin.
I have a typescript project which has uses one of our node modules which normally runs in our front-end. We are now looking to use this module in node on our server.
The module uses es6 import syntax import { props } from 'module/file'
When I include a ref in typescript using either of the following methods
import { props } from 'module/file';
var props = require('module/file');
I get the following error from typescript
unexpected token 'import'
(function (exports, require, module, __filename, __dirname) { import
It's a big job to re-write the module, and I've tried using babel with babel-plugin-dynamic-import-node, as well as SystemJS.
The problem with these systems is that they are all asynchronous, so I can't import the module in the standard fashion, so I would need to do a whole bunch of re-write when we get to the point that I can use import natively in node.js.
I can't be the first person to have this issue, but I can't seem to find a working solution.
--------------- update with set-up -------------
In response to #DanielKhoroshko's response. The original module I am trying to import is normally packaged by webpack in order to use on the front-end. I am now trying to use this same module both server-side and in the front-end (via webpack on the front-end) without re-writing the imports to use require and without running webpack to bundle the js to use on the server.
To be clear, the original module is written in JS, our service which is trying to use this module is written in typescript and transpiled. When the typescript tries to require the old module which uses import, it is at this point that we are running into the issue.
------------------ some progress ---------------------------
I've made some progress by creating a file in my imported module which uses babel in node.js to transpile the es6 code into commonJS modules.
I've done this via
var babel = require("babel-core")
var store = babel.transformFileSync(__dirname + '/store.js', {
plugins: ["transform-es2015-modules-commonjs"]
});
module.exports = {
store: store.code
}
I can now get the store in my new node.js project. However, the submodules within the store.js file are not included in the export.
So where in my module, it says
import activities from './reducers/activities';
I now get an error
Cannot find module './reducers/activities'
How can I get babel to do a deep traversal to include the sub-directories?
unexpected token 'import' means you are running es-modules code in environment that doesn't support import/export commands. If you are writing you code in TypeScript it's important to transpile it first before building for the browser or use ts-node to run it server-side.
If you are using webpack there are loaders ts-loader and awesome-typescript-loader
What is your setup?
To describe the module you would need to create an activities.d.ts file in the same folder where the js-version (I understood it is called activities.js and containers a reducer) resides with the following (approx.):
import { Reducer } from 'redux';
export const activities: Reducer<any>;
#Daniel Khoroshko was right in many ways, I ended up finding #std/esm which lets you import es6 modules and worked find for fetching the included imports as well.
var babel = require('babel-register')({
presets: ["env"]
});
require = require('#std/esm')(module);
var store = require('ayvri-viewer/src/store');
exports.default = {
store: store
}
I had to run babel to get a consistent build from es6 to node compatible es5