I have a file, test.js with these lines of code inside:
import {blabla} from "./bla";
async function dataGenerator() {
..........
}
(async() => {
console.log('1')
await dataGenerator()
console.log('2')
})()
Note: Ignore the import structure. It is just fictive for the question. In my file the imports are auto.
When I'm trying to run from terminal with node test.js it returns error:
Cannot find module 'D:\bla' imported from D:\test.js
I have added into package.json the line: "type": "module". Without this it returns:
Cannot use import statement outside a module
I'm using node v14. How can I run the test.js without adding to all the imports ".js". There are functions in functions in functions and is complicated to add .js extension. Is there any npm to run it?
Node.js by default does not attempt to guess the file extension when using import for ES modules. This is different from CommonJS modules with require.
In the documentation for the ES module loader you can read how files are found on disk.
The heading 'Customizing ESM specifier resolution algorithm' states:
The --experimental-specifier-resolution=[mode] flag can be used to customize the extension resolution algorithm. The default mode is explicit, which requires the full path to a module be provided to the loader. To enable the automatic extension resolution and importing from directories that include an index file use the node mode.
Related
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SyntaxError: Cannot use import statement outside a module
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So I am currently practicing with a trading bot on hardhat. My problem is, when I want to run my script this error shows up:
import './ABIConstants.js';
^^^^^^
SyntaxError: Cannot use import statement outside a module
with this suggestion:
(node:1284) Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension.
However, when I do as it tells me and set "type":"module" I get this error:
hardhat.config.js is treated as an ES module file as it is a .js file whose nearest parent package.json contains "type": "module" which declares all .js files in that package scope as ES modules.
Instead rename hardhat.config.js to end in .cjs, change the requiring code to use dynamic import() which is avakage.json to treat all .js files as CommonJS (using .mjs for all ES modules instead).
And the errors continue as I do the above....etc....
How do I fix this?
Heres the command I am using to run the script if it helps
npx hardhat run scripts/ArbitrageBot.js
There are two kinds of modules in nodejs - the older CommonJS which uses require() to load other CommonJS modules and the newer ESM which uses import to load other ESM modules? There are a few ways to mix and match module types, but that requires some additional knowledge and it is always easier if all the modules in your project are of the same type. So, for us to offer specific advice on your project, we need to know everything that you're trying to use in your project and what module type they all are.
The specific error you first report in your question is because you are trying to use import to load other modules from a file that nodejs is assuming is a CommonJS module and it will not allow that. If everything you are programming with is CommonJS modules, then switch to use require() to load your module instead of import. But, if everything isn't CommonJS modules, then it may be a bit more complicated.
The file extension (.mjs or .cjs) can force a module type or the "type": xxx in package.json can force a type. By default, with neither of those in place nodejs assumes your top level module with a .js extension is a CommonJS module where you would use require() to load other CommonJS modules.
The second error you get when you tried to force your top level module to be an ESM module makes it sounds like the module you are trying to import is a CommonJS module.
So, if I had to guess, I'd say the file you are trying to import is a CommonJS file and therefore, life would be easiest if you made your top level file CommonJS. To do that, remove the "type": "module" from package.json and change your import someModule to require(someModule) instead. This will attempt to just let everything be CommonJS modules.
I am getting the following error when trying to run npm build on my serverless aws-nodejs-typescript project and do not understand how to fix it. Anyone able to point me in the right direction please?
npm build
(node:44390) UnhandledPromiseRejectionWarning: Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: /usr/local/lib/node_modules/npm/node_modules/chalk/source/index.js
require() of ES modules is not supported.
require() of /usr/local/lib/node_modules/npm/node_modules/chalk/source/index.js from /usr/local/lib/node_modules/npm/lib/utils/explain-dep.js is an ES module file as it is a .js file whose nearest parent package.json contains "type": "module" which defines all .js files in that package scope as ES modules.
Instead rename index.js to end in .cjs, change the requiring code to use import(), or remove "type": "module" from /usr/local/lib/node_modules/npm/node_modules/chalk/package.json.
...
Thanks very much!
The latest version of chalk has changed to ES6 import/export syntax instead of CJS (CommonJS with require). So instead of:
const chalk = require('chalk');
You have to do:
import chalk from 'chalk';
You'll (unfortunately) have to change all the other requires into imports as well, then change all your module.exports into export default and all your exports.whatever to export whatever; where whatever is your thing, or as suggested rename your file to index.cjs to force CJS.
Then there are the docs for import and export if you need them.
Then, you need to add type: "module" to package.json. So much for chalk :)
I didn't like that so I used to just use colors intead, but...
I have lot of javascript written to be run by nodejs, but which we ran through the Babel loader at runtime, so that we could write ES syntax -- in particular using import rather than require.
We have a layout like:
package.json
node_modules/
...packages...
top/
server.js
fribbity.js
server.js looks like (I've elided the babel import boilerplate) :
import {fribbity} from 'top/fribbity'
const x = fribbity()
console.log(`fribbity = ${x}`)
while fribbity.js might be
export const fribbity = () => 17
I'd like to promote all this code to use native ES modules in Node 14+. I added "type": "module" to package.json. But now I've run into the module resolution rules. By default, Node now expects my import in server.js to be
import {fribbity} from './fribbity.js'
Are there settings I can apply in package.json, or on the node command line, that would enable node to resolve the imports as they were originally written? That is, preserving the deep import path style (import string begins with no slash or dot, and ends without the ".js" extension)? I've tried several false starts.
I am writing a JavaScript es6 module which contains "Mocha" test-cases which test a JavaScript es6 module containing the actual functionality of my app.
I am trying to import nodejs module "module" via es6 import like so:
import { createRequire } from 'module';
Next I create a "require" function by calling "createRequire":
const require = createRequire(import.meta.url);
Afterwards I try to use "require" to import nodejs modules:
const chai = require('chai');
const assert = chai.assert;
I put that all together in a HTML file, started a web-server and opened the HTML file in the browser.
Unfortunately, the first line gives me an error in the console of the Browser Firefox:
TypeError: Error resolving module specifier: module
The browser Chromium gives me the following error message:
Uncaught TypeError: Failed to resolve module specifier "module". Relative references must start with either "/", "./", or "../".
Actually, giving relative references is not working either:
I installed the nodejs module "module" (npm install module) and used a relative path to that module. Unfortunately, the browser does not know how to load the module because no concrete entrypoint is given.
I just tried stick to the manual but had no luck:
https://nodejs.org/api/modules.html#modules_module_createrequire_filename
What do you think? How should I change my code so that this works?
Many thanks in advance for your valuable advice.
I hope you've installed the module using 'npm install module' command, try using commonJS pattern and include the module in the following way
const { createRequire } = require('module');
require() is used to load files in node, and module is a node module.
These things don't exist in browsers.
You do these things, and running mocha tests in node. There should be no browser, just a command line.
I have created some npm modules and compile them to:
commonJS (using exports.default =) and
esm (using export default)
I set up my package.json like so:
main: "index.cjs.js",
module: "index.esm.js"
When I npm install the package and I simple import it like:
import myPackage from 'my-package'
It will automatically choose the main file, not the module.
My question:
Is there a way to import the module file instead when doing import myPackage from 'my-package' in a JavaScript file?
Why I choose the commonJS file for "main":
I noticed that using Node, importing an esm file is not possible because of export default, it has to be commonJS. I have some simple helper JS functions like this and this, and I would want them to be usable to the widest audience. That's why I chose cjs for the "main" path in package.json.
Why I define a separate "module" in package.json:
Lots of famous libraries like Vue.js are already doing this. See further information on this Stackoverflow thread:
What is the "module" package.json field for?
Why do I want to be able to import the "module" file instead of the "main" file:
There is currently a bug in Rollup where it will not properly show JSDoc comments when coding after having imported a cjs file, but it does work when importing a es file.
The workaround I want to avoid:
Just set "main" to the esm file in package.json, right? But then all users who are using my packages in Node apps will not be able to use it anymore...
→ I'm really confused about all this as well, but I think I did enough research to make sense of all it. That being said, if anyone knows a better approach or any other advice, please do tell me in the comments down below!!
Just don't use extension for main file and have es6 and CommonJS version as two separate files with the same name and in the same directory, but with different extension, so:
index.js // transpiled CommonJS code for old nodejs
index.mjs // es6 module syntax
and in package.json:
{
"main": "index"
}
If node is launched with --experimental-modules flag, it would use *.mjs file, otherwise *.js.
Nodejs does not support "module" but does support the newer "exports" spec.
https://nodejs.org/api/packages.html#exports
https://github.com/nodejs/node/blob/v16.14.0/lib/internal/modules/esm/resolve.js#L910
"exports": {
"import": "./main-module.js",
"require": "./main-require.cjs"
},