Develop Reference

Node Error Must use import to load ES module

I have the following code:
import { toString } from 'nlcst-to-string';
import { retext } from 'retext';
import retextPos from 'retext-pos';
import retextKeywords from 'retext-keywords';
const sentence =
"President Obama woke up Monday facing a Congressional defeat that many in both parties believed could hobble his presidency."
function process(params) {
// some code
}
exports.main = processComment;
But I am getting the following error:
[ERR_REQUIRE_ESM]: Must use import to load ES module
Which is strange because I already am using import.
I have also tried adding "type": "module" to package.json - no luck. Tried ending the file extension in .mjs - nothing

It’s either your node version or None of your import locations have ./
Even if those files are in the same directory as your main js file you still need that.
Unless that’s so npm library I have never heard of.

Check your node version. Node version 14+ supports the type: "module"
node --version
If you have node version manager, you can run
nvm install your_desired_version_here
to get a compliant version

How to prevent typescript from transpiling dynamic imports into require()?

I'm building a discord.js Discord bot. Now for some reason, discord.js doesn't work with ESM modules (a totally separate issue), so my bot app uses CommonJS modules. Now I have another project on my system called Lib, which has a lot of utility functions that I plan to use in several different projects so I don't have to rewrite them. This Lib project uses ESM modules. Since I have to import Lib from DiscordBot, I use the dynamic import syntax in typescript. Now, whenever I transpile my DiscordBot project, the dynamic imports get converted into some ugly javascript module code, and that ugly module code ultimately ends up using require(). Since require() can't import ESM modules, my bot ends up crashing.
I tried however to stop my ts compiler, copy the code from my ts file that imports Lib then pasting that code into the corresponding JS file manually (and removing TS-exclusive features like type annotations and interfaces). Then I ran my bot app, and it worked perfectly fine. But I don't want to have to do this every time. So it's tsc's compiling that's the problem. How do I fix this?

So I understand the purpose is:
Develop the code in TypeScript
Run the compiled code in CommonJS package
Import and use an ES Module
Option 1:
If "module" in tsconfig.json is set to "commonjs", currently there's no way to prevent TypeScript from transpiling dynamic import() into require() - except that you hide the code in a string and use eval to execute it. Like this:
async function body (pMap:any){
// do something with module pMap here
}
eval ("import('p-map').then(body)");
No way TypeScript transpiles a string!
Option 2
Set "module" in tsconfig.json to "es2020". By doing this, dynamic import would not be transpiled into require(), and you can use dynamic import to import a CommonJS or ES Module. Or, you can use the const someModule = require("someModule") syntax to import a CommonJS module (would not be transpiled to ES6 import syntax). You cannot use the ES6 import syntax such as import * as someModule from "someModule" or import someModule from "someModule". These syntaxes will emit ES Module syntax imports ("module" is set to "es2020") and cannot be run in CommonJS package.
Below is a bit information:
If "module" is set to "es2020": dynamic import import() is not transpiled.
If "module" is set to `"es2015": there's an error:
TS1323: Dynamic imports are only supported when the '--module' flag is set to 'es2020', 'esnext', 'commonjs', 'amd', 'system', or 'umd'.
If "module" is set to "commonjs": dynamic imports are transpiled.
Quote tsconfig.json reference for "module" field:
If you are wondering about the difference between ES2015 and ES2020,
ES2020 adds support for dynamic imports, and import.meta.

This is currently not possible. There is a very new issue at GitHub (https://github.com/microsoft/TypeScript/issues/43329), but that is not implemented yet. So everything you can do now is to switch from ESM to CommonJS with your Lib project.
Update 2022
The issue has been closed and there is now a new option for "module" called node12. That should fix the problem

The node12 setting others are talking about did not work for me, but these compilerOptions did, using Typescript 4.7.2:
"module": "CommonJS",
"moduleResolution": "Node16",
This saved my backside, I did not have to migrate all import requires to imports to be able to use an ESM npm lib.
Typescript input source:
import Redis = require('redis');
import * as _ from 'lodash';
export async function main() {
const fileType = await import('file-type');
console.log(fileType, _.get, Redis);
}
CommonJS output:
...
const Redis = require("redis");
const _ = __importStar(require("lodash"));
async function main() {
const fileType = await import('file-type');
console.log(fileType, _.get, Redis);
}
exports.main = main;

What compiler/bundler are you using? I am assuming tsc based on context.
I recommend using esbuild to compile and bundle your TS. You can also use it simply to transform it after using tsc. It has an option called "format" that can remove any module-style imports. See https://esbuild.github.io/api/#format.
Here is a simple example of using.
build.js
const esbuild = require("esbuild");
esbuild.build({
allowOverwrite: true,
write: true,
entryPoints: ["my-main-file.ts"],
outfile: "some-file.bundle.js",
format: "cjs", //format option set to cjs makes all imports common-js style
bundle: true,
}).then(() => {
console.log("Done!");
});
You can then add something like this to your package.json
"scripts": {
"build": "node build.js",
...rest of scripts
Here is an additional link about some caveats using esbuild with typescript. None of these should really be a problem for you. https://esbuild.github.io/content-types/#typescript-caveats

This has been fixed with the addition of the node12 option for the module setting. From the docs:
Available in nightly builds, the experimental node12 and nodenext modes integrate with Node’s native ECMAScript Module support. The emitted JavaScript uses either CommonJS or ES2020 output depending on the file extension and the value of the type setting in the nearest package.json. Module resolution also works differently. You can learn more in the handbook.
If you use this setting without a nightly build, however, it currently produces the following error:
error TS4124: Compiler option 'module' of value 'node12' is unstable. Use nightly TypeScript to silence this error. Try updating with 'npm install -D typescript#next'.

I'm using a variant of the already mentioned eval-based hack to overcome this issue.
So for example, parse-domain is distributed as an ESM module, so importing it like this breaks in a CJS-based node app:
import { fromUrl, parseDomain } from 'parse-domain';
const parseDomainFromUrl = (url: string) => {
return parseDomain(fromUrl(url));
}
And this is how I have managed to get it working:
const dynamicImport = new Function('specifier', 'return import(specifier)');
const parseDomainFromUrl = (url: string) => {
return dynamicImport('parse-domain').then((module: any) => {
const { fromUrl, parseDomain } = module;
return parseDomain(fromUrl(url));
})
};
(Note that parseDomainFromUrl became asynchronous in the process, so it would need to be awaited by the caller.)

Promoting Babelized ES module code to native Node 14+

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.

SyntaxError: Cannot use import statement outside a module

I've got an ApolloServer project that's giving me trouble, so I thought I might update it and ran into issues when using the latest Babel. My "index.js" is:
require('dotenv').config()
import {startServer} from './server'
startServer()
And when I run it I get the error
SyntaxError: Cannot use import statement outside a module
First I tried doing things to convince TPTB* that this was a module (with no success). So I changed the "import" to a "require" and this worked.
But now I have about two dozen "imports" in other files giving me the same error.
*I'm sure the root of my problem is that I'm not even sure what's complaining about the issue. I sort of assumed it was Babel 7 (since I'm coming from Babel 6 and I had to change the presets) but I'm not 100% sure.
Most of what I've found for solutions don't seem to apply to straight Node. Like this one here:
ES6 module Import giving "Uncaught SyntaxError: Unexpected identifier"
Says it was resolved by adding "type=module" but this would typically go in the HTML, of which I have none. I've also tried using my project's old presets:
"presets": ["es2015", "stage-2"],
"plugins": []
But that gets me another error: "Error: Plugin/Preset files are not allowed to export objects, only functions."
Here are the dependencies I started with:
"dependencies": {
"#babel/polyfill": "^7.6.0",
"apollo-link-error": "^1.1.12",
"apollo-link-http": "^1.5.16",
"apollo-server": "^2.9.6",
"babel-preset-es2015": "^6.24.1",

Verify that you have the latest version of Node.js installed (or, at least 13.2.0+). Then do one of the following, as described in the documentation:
Option 1
In the nearest parent package.json file, add the top-level "type" field with a value of "module". This will ensure that all .js and .mjs files are interpreted as ES modules. You can interpret individual files as CommonJS by using the .cjs extension.
// package.json
{
"type": "module"
}
Option 2
Explicitly name files with the .mjs extension. All other files, such as .js will be interpreted as CommonJS, which is the default if type is not defined in package.json.

If anyone is running into this issue with TypeScript, the key to solving it for me was changing
"target": "esnext",
"module": "esnext",
to
"target": "esnext",
"module": "commonjs",
In my tsconfig.json. I was under the impression "esnext" was the "best", but that was just a mistake.

For those who were as confused as I was when reading the answers, in your package.json file, add
"type": "module"
in the upper level as show below:
{
"name": "my-app",
"version": "0.0.0",
"type": "module",
"scripts": { ...
},
...
}

According to the official documentation:
import statements are permitted only in ES modules. For similar functionality in CommonJS, see import().
To make Node.js treat your file as an ES module, you need to (Enabling):
add "type": "module" to package.json
add "--experimental-modules" flag to the Node.js call

I ran into the same issue and it's even worse: I needed both "import" and "require"
Some newer ES6 modules works only with import.
Some CommonJS works with require.
Here is what worked for me:
Turn your js file into .mjs as suggested in other answers
"require" is not defined with the ES6 module, so you can define it this way:
import { createRequire } from 'module'
const require = createRequire(import.meta.url);
Now 'require' can be used in the usual way.
Use import for ES6 modules and require for CommonJS.
Some useful links: Node.js's own documentation. difference between import and require. Mozilla has some nice documentation about import

I had the same issue and the following has fixed it (using Node.js 12.13.1):
Change .js files extension to .mjs
Add --experimental-modules flag upon running your app.
Optional: add "type": "module" in your package.json
More information: https://nodejs.org/api/esm.html

First we'll install #babel/cli, #babel/core and #babel/preset-env:
npm install --save-dev #babel/cli #babel/core #babel/preset-env
Then we'll create a .babelrc file for configuring Babel:
touch .babelrc
This will host any options we might want to configure Babel with:
{
"presets": ["#babel/preset-env"]
}
With recent changes to Babel, you will need to transpile your ES6 before Node.js can run it.
So, we'll add our first script, build, in file package.json.
"scripts": {
"build": "babel index.js -d dist"
}
Then we'll add our start script in file package.json.
"scripts": {
"build": "babel index.js -d dist", // replace index.js with your filename
"start": "npm run build && node dist/index.js"
}
Now let's start our server.
npm start

I Tried with all the methods, but nothing worked.
I got one reference from GitHub.
To use TypeScript imports with Node.js, I installed the below packages.
1. npm i typescript --save-dev
2. npm i ts-node --save-dev
Won't require type: module in package.json
For example,
{
"name": "my-app",
"version": "0.0.1",
"description": "",
"scripts": {
},
"dependencies": {
"knex": "^0.16.3",
"pg": "^7.9.0",
"ts-node": "^8.1.0",
"typescript": "^3.3.4000"
}
}

Step 1
yarn add esm
or
npm i esm --save
Step 2
package.json
"scripts": {
"start": "node -r esm src/index.js",
}
Step 3
nodemon --exec npm start

Node v14.16.0
For those who've tried .mjs and got:
Aviator#AW:/mnt/c/Users/Adrian/Desktop/Programming/nodejs_ex$ node just_js.mjs
file:///mnt/c/Users/Adrian/Desktop/Programming/nodejs_ex/just_js.mjs:3
import fetch from "node-fetch";
^^^^^
SyntaxError: Unexpected identifier
and who've tried import fetch from "node-fetch";
and who've tried const fetch = require('node-fetch');
Aviator#AW:/mnt/c/Users/Adrian/Desktop/Programming/nodejs_ex$ node just_js.js
(node:4899) Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension.
(Use `node --trace-warnings ...` to show where the warning was created)
/mnt/c/Users/Adrian/Desktop/Programming/nodejs_ex/just_js.js:3
import fetch from "node-fetch";
^^^^^^
SyntaxError: Cannot use import statement outside a module
and who've tried "type": "module" to package.json, yet continue seeing the error,
{
"name": "test",
"version": "1.0.0",
"description": "to get fetch working",
"main": "just_js.js",
"type": "module",
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1"
},
"author": "",
"license": "MIT"
}
I was able to switch to axios without a problem.
import axios from 'axios'; <-- put at top of file.
Example:
axios.get('https://www.w3schools.com/xml/note.xml').then(resp => {
console.log(resp.data);
});

I found the 2020 update to the answer in this link helpful to answering this question as well as telling you WHY it does this:
Using Node.js require vs. ES6 import/export
Here's an excerpt:
"Update 2020
Since Node v12, support for ES modules is enabled by default, but it's still experimental at the time of writing this. Files including node modules must either end in .mjs or the nearest package.json file must contain "type": "module". The Node documentation has a ton more information, also about interop between CommonJS and ES modules."

I'm new to Node.js, and I got the same issue for the AWS Lambda function (using Node.js) while fixing it.
I found some of the differences between CommonJS and ES6 JavaScript:
ES6:
Add "type":"module" in the package.json file
Use "import" to use from lib.
Example: import jwt_decode from jwt-decode
Lambda handler method code should be define like this
"exports.handler = async (event) => { }"
CommonJS:
Don't add "type":"module" in the package.json file
Use "require" to use from lib.
Example: const jwt_decode = require("jwt-decode");
The lambda handler method code should be defines like this:
"export const handler = async (event) => { }"

In my case. I think the problem is in the standard node executable. node target.ts
I replaced it with nodemon and surprisingly it worked!
The way using the standard executable (runner):
node target.ts
The way using the nodemon executable (runner):
nodemon target.ts
Do not forget to install nodemon with npm install nodemon ;P
Note: this works amazing for development. But, for runtime, you may execute node with the compiled js file!

To use import, do one of the following.
Rename the .js file to .mjs
In package.json file, add {type:module}

If you are using ES6 JavaScript imports:
install cross-env
in package.json change "test": "jest" to "test": "cross-env NODE_OPTIONS=--experimental-vm-modules jest"
more in package.json, add these:
...,
"jest": {
"transform": {}
},
"type": "module"
Explanation:
cross-env allows to change environment variables without changing the npm command. Next, in file package.json you change your npm command to enable experimental ES6 support for Jest, and configure Jest to do it.

This error also comes when you run the command
node filename.ts
and not
node filename.js
Simply put, with the node command we will have to run the JavaScript file (filename.js) and not the TypeScript file unless we are using a package like ts-node.

If you want to use BABEL, I have a simple solution for that!
Remember this is for nodejs example: like an expressJS server!
If you are going to use react or another framework, look in the babel documentation!
First, install (do not install unnecessary things that will only trash your project!)
npm install --save-dev #babel/core #babel/node
Just 2 WAO
then config your babel file in your repo!
file name:
babel.config.json
{
"presets": ["#babel/preset-env"]
}
if you don't want to use the babel file, use:
Run in your console, and script.js is your entry point!
npx babel-node --presets #babel/preset-env -- script.js
the full information is here; https://babeljs.io/docs/en/babel-node

I had this error in my NX workspace after upgrading manually. The following change in each jest.config.js fixed it:
transform: {
'^.+\\.(ts|js|html)$': 'jest-preset-angular',
},
to
transform: {
'^.+\\.(ts|mjs|js|html)$': 'jest-preset-angular',
},

I had this issue when I was running migration
Its es5 vs es6 issue
Here is how I solved it
I run
npm install #babel/register
and add
require("#babel/register")
at the top of my .sequelizerc file my
and go ahead to run my sequelize migrate.
This is applicable to other things apart from sequelize
babel does the transpiling

Just add --presets '#babel/preset-env'.
For example,
babel-node --trace-deprecation --presets '#babel/preset-env' ./yourscript.js
Or
in babel.config.js
module.exports = {
presets: ['#babel/preset-env'],
};

To make your import work and avoid other issues, like modules not working in Node.js, just note that:
With ES6 modules you can not yet import directories. Your import should look like this:
import fs from './../node_modules/file-system/file-system.js'

For people coming to this thread due to this error in Netlify functions even after adding "type": "module" in package.json file, update your netlify.toml to use 'esbuild'. Since esbuild supports ES6, it would work.
[functions]
node_bundler = "esbuild"
Reference:
https://docs.netlify.com/functions/build-with-javascript/#automated-dependency-bundling

The documentation is confusing. I use Node.js to perform some local task in my computer.
Let's suppose my old script was test.js. Within it, if I want to use
import something from "./mylocalECMAmodule";
it will throw an error like this:
(node:16012) Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension.
SyntaxError: Cannot use import statement outside a module
...
This is not a module error, but a Node.js error. Forbid loading anything outside a 'module'.
To fix this, just rename your old script test.js into test.mjs.
That's all.

My solution was to include babel-node path while running nodemon as follows:
nodemon node_modules/.bin/babel-node index.js
You can add in your package.json script as:
debug: nodemon node_modules/.bin/babel-node index.js
NOTE: My entry file is index.js. Replace it with your entry file (many have app.js/server.js).

I had the same problem when I started to use Babel... But later, I
had a solution... I haven't had the problem any more so far...
Currently, Node.js v12.14.1, "#babel/node": "^7.8.4", I use babel-node and nodemon to execute (Node.js is fine as well..)
package.json: "start": "nodemon --exec babel-node server.js "debug": "babel-node debug server.js"!! Note: server.js is my entry
file, and you can use yours.
launch.json. When you debug, you also need to configure your launch.json file "runtimeExecutable":
"${workspaceRoot}/node_modules/.bin/babel-node"!! Note: plus
runtimeExecutable into the configuration.
Of course, with babel-node, you also normally need and edit another file, such as the babel.config.js/.babelrc file

In case you're running nodemon for the Node.js version 12, use this command.
server.js is the "main" inside package.json file, replace it with the relevant file inside your package.json file:
nodemon --experimental-modules server.js

I recently had the issue. The fix which worked for me was to add this to file babel.config.json in the plugins section:
["#babel/plugin-transform-modules-commonjs", {
"allowTopLevelThis": true,
"loose": true,
"lazy": true
}],
I had some imported module with // and the error "cannot use import outside a module".

If you are using node, you should refer to this document. Just setup babel in your node app it will work and It worked for me.
npm install --save-dev #babel/cli #babel/core #babel/preset-env

When I used sequelize migrations with npx sequelize db:migrate, I got this error, so my solution for this was adding the line require('#babel/register'); into the .sequelizerc file as the following image shows:
Be aware you must install Babel and Babel register.

Wrong MIME-Type for JavaScript Module Files
The common source of the problem is the MIME-type for "Module" type JavaScript files is not recognized as a "module" type by the server, the client, or the ECMAScript engine that process or deliver these files.
The problem is the developers of Module JavaScript files incorrectly associated Modules with a new ".mjs" (.js) extension, but then assigned it a MIME-type server type of "text/javascript". This means both .js and .mjs types are the same. In fact the new type for .js JavaScript files has also changed to "application/javascript", further confusing the issue. So Module JavaScript files are not being recognized by any of these systems, regardless of Node.js or Babel file processing systems in development.
The main problem is this new "module" subtype of JavaScript is yet known to most servers or clients (modern HTML5 browsers). In other words, they have no way to know what a Module file type truly is apart from a JavaScript type!
So, you get the response you posted, where the JavaScript engine is saying it needs to know if the file is a Module type of JavaScript file.
The only solution, for server or client, is to change your server or browser to deliver a new Mime-type that trigger ES6 support of Module files, which have an .mjs extension. Right now, the only way to do that is to either create a HTTP content-type on the server of "module" for any file with a .mjs extension and change your file extension on module JavaScript files to ".mjs", or have an HTML script tag with type="module" added to any external <script> element you use that downloads your external .js JavaScript module file.
Once you fool the browser or JavaScript engines into accepting the new Module file type, they will start doing their scripting circus tricks in the JS engines or Node.js systems you use.

Publish ES module (.mjs) to NPMJS, with backwards compatibility for Node <8.5.0 (Dual Package)

Up to Node v8.5.0, publishing a module written in ES6 to NPMJS was a straightforward process: transpile the ES6 code using a tool like Babel, and publish to NPMJS the resulting lib directory, while your GitHub repo contains the src files.
With v8.5.0, Node has released experimental support for native modules (export/import) via the --experimental-modules flag. It is now possible to publish purely-ES6 modules to NPMJS, and use them without any transpilation, as long as the files involved have an .mjs extension.
How can I publish an ES6 module (.mjs) so that it can also be used with older Node versions, which don't support ES native modules?

This is possible with 13.7.0+ using conditional exports (which as of 13.10.0+ are no longer experimental). It's not well documented or obvious how to do this in a completely backwards-compatible way, but here's the trick which I previously researched back when it was experiemental:
node_modules/mod/package.json
{
"main": "./lib.js",
"exports": {
".": [
{
"import": "./lib.mjs",
"require": "./lib.js",
"default": "./lib.js"
},
"./lib.js"
]
}
}
node_modules/mod/lib.js
exports.format = 'cjs';
node_modules/mod/lib.mjs
export const format = 'mjs';
Now it's possible to use both CommonJS:
main.js
const {format} = require('mod');
console.log(format);
$ node main.js
cjs
And ES Modules:
main.mjs
import {format} from 'mod';
console.log(format);
$ node main.mjs
mjs
Prior to this is was possible at one point to just use an extension-less main entry in package.json, but this feature was removed. See the revision history on this answer if interested.