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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.
I don't understand what is wrong.
Node v5.6.0
NPM v3.10.6
The code:
function (exports, require, module, __filename, __dirname) {
import express from 'express'
};
The error:
SyntaxError: Unexpected token import
at exports.runInThisContext (vm.js:53:16)
at Module._compile (module.js:387:25)
at Object.Module._extensions..js (module.js:422:10)
at Module.load (module.js:357:32)
at Function.Module._load (module.js:314:12)
at Function.Module.runMain (module.js:447:10)
at startup (node.js:140:18)
at node.js:1001:3
Node 13+ Since Node 13, you can use either the .mjs extension, or set {"type": "module"} in your package.json. You don't need to use the --experimental-modules flag. Modules is now marked as stable in node.js
Node 12 Since Node 12, you can use either the .mjs extension, or set "type": "module" in your package.json. And you need to run node with the --experimental-modules flag.
Node 9 In Node 9, it is enabled behind a flag, and uses the .mjs extension.
node --experimental-modules my-app.mjs
While import is indeed part of ES6, it is unfortunately not yet supported in NodeJS by default, and has only very recently landed support in browsers.
See browser compat table on MDN and this Node issue.
From James M Snell's Update on ES6 Modules in Node.js (February 2017):
Work is in progress but it is going to take some time — We’re currently looking at around a year at least.
Until support shows up natively (now marked stable in Node 13+), you'll have to continue using classic require statements:
const express = require("express");
If you really want to use new ES6/7 features in NodeJS, you can compile it using Babel. Here's an example server.
Unfortunately, Node.js doesn't support ES6's import yet.
To accomplish what you're trying to do (import the Express module), this code should suffice
var express = require("express");
Also, be sure you have Express installed by running
$ npm install express
See the Node.js Docs for more information about learning Node.js.
I'm shocked esm hasn't been mentioned. This small, but mighty package allows you to use either import or require.
Install esm in your project
$ npm install --save esm
Update your Node Start Script to use esm
node -r esm app.js
esm just works. I wasted a TON of time with .mjs and --experimental-modules only to find out a .mjs file cannot import a file that uses require or module.exports. This was a huge problem, whereas esm allows you to mix and match and it just figures it out... esm just works.
As mentioned in other answers Node JS currently doesn't support ES6 imports.
(As of now, read EDIT 2)
Enable ES6 imports in node js provides a solution to this issue. I have tried this and it worked for me.
Run the command:
npm install babel-register babel-preset-env --save-dev
Now you need to create a new file (config.js) and add the following code to it.
require('babel-register')({
presets: [ 'env' ]
})
// Import the rest of our application.
module.exports = require('./your_server_file.js')
Now you can write import statements without getting any errors.
Hope this helps.
EDIT:
You need to run the new file which you created with above code. In my case it was config.js. So I have to run:
node config.js
EDIT 2:
While experimenting, I found one easy solution to this issue.
Create .babelrc file in the root of your project.
Add following (and any other babel presets you need, can be added in this file):
{
"presets": ["env"]
}
Install babel-preset-env using command npm install babel-preset-env --save, and then install babel-cli using command npm install babel-cli -g --save
Now, go to the folder where your server or index file exists and run using:
babel-node fileName.js
Or you can run using npm start by adding following code to your package.json file:
"scripts": {
"start": "babel-node src/index.js"
}
Error: SyntaxError: Unexpected token import or SyntaxError: Unexpected token export
Solution: Change all your imports as example
const express = require('express');
const webpack = require('webpack');
const path = require('path');
const config = require('../webpack.config.dev');
const open = require('open');
And also change your export default = foo; to module.exports = foo;
In case that you still can't use "import" here is how I handled it:
Just translate it to a node friendly require. Example:
import { parse } from 'node-html-parser';
Is the same as:
const parse = require('node-html-parser').parse;
babel 7 proposal
can you add dev dependencies
npm i -D #babel/core #babel/preset-env #babel/register
and add a .babelrc in the root
{
"presets": [
[
"#babel/preset-env",
{
"targets": {
"node": "current"
}
}
]
]
}
and add to the .js file
require("#babel/register")
or if you run it in the cli, you could use the require hook as -r #babel/register, ex.
$node -r #babel/register executeMyFileWithESModules.js
When I was started with express always wanted a solution to use import instead require
const express = require("express");
// to
import express from "express"
Many time go through this line:- Unfortunately, Node.js doesn't support ES6's import yet.
Now to help other I create new two solutions here
1) esm:-
The brilliantly simple, babel-less, bundle-less ECMAScript module loader.
let's make it work
yarn add esm / npm install esm
create start.js or use your namespace
require = require("esm")(module/*, options*/)
// Import the rest of our application.
module.exports = require('./src/server.js')
// where server.js is express server start file
Change in your package.josn pass path of start.js
"scripts": {
"start": "node start.js",
"start:dev": "nodemon start.js",
},
"dependencies": {
+ "esm": "^3.2.25",
},
"devDependencies": {
+ "nodemon": "^1.19.2"
}
2) Babel js:-
This can be divide into 2 part
a) Solution 1 thanks to timonweb.com
b) Solution 2
use Babel 6 (older version of babel-preset-stage-3 ^6.0)
create .babelrc file at your root folder
{
"presets": ["env", "stage-3"]
}
Install babel-preset-stage-3
yarn add babel-cli babel-polyfill babel-preset-env bable-preset-stage-3 nodemon --dev
Change in package.json
"scripts": {
+ "start:dev": "nodemon --exec babel-node -- ./src/index.js",
+ "start": "npm run build && node ./build/index.js",
+ "build": "npm run clean && babel src -d build -s --source-maps --copy-files",
+ "clean": "rm -rf build && mkdir build"
},
"devDependencies": {
+ "babel-cli": "^6.26.0",
+ "babel-polyfill": "^6.26.0",
+ "babel-preset-env": "^1.7.0",
+ "babel-preset-stage-3": "^6.24.1",
+ "nodemon": "^1.19.4"
},
Start your server
yarn start / npm start
Oooh no we create new problem
regeneratorRuntime.mark(function _callee(email, password) {
^
ReferenceError: regeneratorRuntime is not defined
This error only come when you use async/await in your code.
Then use polyfill that includes a custom regenerator runtime and core-js.
add on top of index.js
import "babel-polyfill"
This allow you to use async/await
use Babel 7
Need to upto date every thing in your project
let start with babel 7
.babelrc
{
"presets": ["#babel/preset-env"]
}
Some change in package.json
"scripts": {
+ "start:dev": "nodemon --exec babel-node -- ./src/index.js",
+ "start": "npm run build && node ./build/index.js",
+ "build": "npm run clean && babel src -d build -s --source-maps --copy-files",
+ "clean": "rm -rf build && mkdir build",
....
}
"devDependencies": {
+ "#babel/cli": "^7.0.0",
+ "#babel/core": "^7.6.4",
+ "#babel/node": "^7.0.0",
+ "#babel/polyfill": "^7.0.0",
+ "#babel/preset-env": "^7.0.0",
+ "nodemon": "^1.19.4"
....
}
and use import "#babel/polyfill" on start point
import "#babel/polyfill"
import express from 'express'
const app = express()
//GET request
app.get('/', async (req, res) {
// await operation
res.send('hello world')
})
app.listen(4000, () => console.log('🚀 Server listening on port 400!'))
Are you thinking why start:dev
Seriously. It is good question if you are new. Every change you are boar with start server every time
then use yarn start:dev as development server every change restart server automatically for more on nodemon
if you can use 'babel', try to add build scripts in package.json(--presets=es2015) as below. it make to precompile import code to es2015
"build": "babel server --out-dir build --presets=es2015 && webpack"
As of Node.js v12 (and this is probably fairly stable now, but still marked "experimental"), you have a couple of options for using ESM (ECMAScript Modules) in Node.js (for files, there's a third way for evaling strings), here's what the documentation 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.
Node.js will treat as CommonJS all other forms of input, such as .js files
where the nearest parent package.json file contains no top-level "type"
field, or string input without the flag --input-type. This behavior is to
preserve backward compatibility. However, now that Node.js supports both
CommonJS and ES modules, it is best to be explicit whenever possible. Node.js
will treat the following as CommonJS when passed to node as the initial input,
or when referenced by import statements within ES module code:
Files ending in .cjs.
Files ending in .js, or extensionless files, when the nearest parent
package.json file contains a top-level field "type" with a value of
"commonjs".
Strings passed in as an argument to --eval or --print, or piped to
node via STDIN, with the flag --input-type=commonjs.
I'm going to address another problem within the original question that no one else has. After recently converting from CommonJS to ESM in my own NodeJS project, I've seen very little discussion about the fact that you cannot place imports wherever you want, like you could with require. My project is working great with imports now, but when I use the code in the question, I first get an error for not having a named function. After naming the function, I receive the following...
import express from 'express'
^^^^^^^
SyntaxError: Unexpected identifier
at Loader.moduleStrategy (internal/modules/esm/translators.js:88:18)
You cannot place imports inside functions like you could require. They have to be placed at the top of the file, outside code blocks. I wasted quite a bit of time on this issue myself.
So while all of the above answers are great at helping you get imports to work in your project, none address the fact that the code in the original question cannot work as written.
import statements are supported in the stable release of Node since version 14.x LTS.
All you need to do is specify "type": "module" in package.json.
In my case it was looking after .babelrc file, and it should contain something like this:
{
"presets": ["es2015-node5", "stage-3"],
"plugins": []
}
My project uses node v10.21.0, which still does not support ES6 import keyword. There are multiple ways to make node recognize import, one of them is to start node with node --experimental-modules index.mjs (The mjs extension is already covered in one of the answers here). But, this way, you will not be able to use node specific keyword like require in your code. If there is need to use both nodejs's require keyword along with ES6's import, then the way out is to use the esm npm package. After adding esm package as a dependency, node needs to be started with a special configuration like: node -r esm index.js
I've been trying to get this working. Here's what works:
Use a recent node version. I'm using v14.15.5. Verify your version by running: node --version
Name the files so that they all end with .mjs rather than .js
Example:
mod.mjs
export const STR = 'Hello World'
test.mjs
import {STR} from './mod.mjs'
console.log(STR)
Run: node test.mjs
You should see "Hello World".
Simply install a higher version of Node. As till Node v10 es6 is not supported. You need to disable a few flags or use
I don't understand what is wrong.
Node v5.6.0
NPM v3.10.6
The code:
function (exports, require, module, __filename, __dirname) {
import express from 'express'
};
The error:
SyntaxError: Unexpected token import
at exports.runInThisContext (vm.js:53:16)
at Module._compile (module.js:387:25)
at Object.Module._extensions..js (module.js:422:10)
at Module.load (module.js:357:32)
at Function.Module._load (module.js:314:12)
at Function.Module.runMain (module.js:447:10)
at startup (node.js:140:18)
at node.js:1001:3
Node 13+ Since Node 13, you can use either the .mjs extension, or set {"type": "module"} in your package.json. You don't need to use the --experimental-modules flag. Modules is now marked as stable in node.js
Node 12 Since Node 12, you can use either the .mjs extension, or set "type": "module" in your package.json. And you need to run node with the --experimental-modules flag.
Node 9 In Node 9, it is enabled behind a flag, and uses the .mjs extension.
node --experimental-modules my-app.mjs
While import is indeed part of ES6, it is unfortunately not yet supported in NodeJS by default, and has only very recently landed support in browsers.
See browser compat table on MDN and this Node issue.
From James M Snell's Update on ES6 Modules in Node.js (February 2017):
Work is in progress but it is going to take some time — We’re currently looking at around a year at least.
Until support shows up natively (now marked stable in Node 13+), you'll have to continue using classic require statements:
const express = require("express");
If you really want to use new ES6/7 features in NodeJS, you can compile it using Babel. Here's an example server.
Unfortunately, Node.js doesn't support ES6's import yet.
To accomplish what you're trying to do (import the Express module), this code should suffice
var express = require("express");
Also, be sure you have Express installed by running
$ npm install express
See the Node.js Docs for more information about learning Node.js.
I'm shocked esm hasn't been mentioned. This small, but mighty package allows you to use either import or require.
Install esm in your project
$ npm install --save esm
Update your Node Start Script to use esm
node -r esm app.js
esm just works. I wasted a TON of time with .mjs and --experimental-modules only to find out a .mjs file cannot import a file that uses require or module.exports. This was a huge problem, whereas esm allows you to mix and match and it just figures it out... esm just works.
As mentioned in other answers Node JS currently doesn't support ES6 imports.
(As of now, read EDIT 2)
Enable ES6 imports in node js provides a solution to this issue. I have tried this and it worked for me.
Run the command:
npm install babel-register babel-preset-env --save-dev
Now you need to create a new file (config.js) and add the following code to it.
require('babel-register')({
presets: [ 'env' ]
})
// Import the rest of our application.
module.exports = require('./your_server_file.js')
Now you can write import statements without getting any errors.
Hope this helps.
EDIT:
You need to run the new file which you created with above code. In my case it was config.js. So I have to run:
node config.js
EDIT 2:
While experimenting, I found one easy solution to this issue.
Create .babelrc file in the root of your project.
Add following (and any other babel presets you need, can be added in this file):
{
"presets": ["env"]
}
Install babel-preset-env using command npm install babel-preset-env --save, and then install babel-cli using command npm install babel-cli -g --save
Now, go to the folder where your server or index file exists and run using:
babel-node fileName.js
Or you can run using npm start by adding following code to your package.json file:
"scripts": {
"start": "babel-node src/index.js"
}
Error: SyntaxError: Unexpected token import or SyntaxError: Unexpected token export
Solution: Change all your imports as example
const express = require('express');
const webpack = require('webpack');
const path = require('path');
const config = require('../webpack.config.dev');
const open = require('open');
And also change your export default = foo; to module.exports = foo;
In case that you still can't use "import" here is how I handled it:
Just translate it to a node friendly require. Example:
import { parse } from 'node-html-parser';
Is the same as:
const parse = require('node-html-parser').parse;
babel 7 proposal
can you add dev dependencies
npm i -D #babel/core #babel/preset-env #babel/register
and add a .babelrc in the root
{
"presets": [
[
"#babel/preset-env",
{
"targets": {
"node": "current"
}
}
]
]
}
and add to the .js file
require("#babel/register")
or if you run it in the cli, you could use the require hook as -r #babel/register, ex.
$node -r #babel/register executeMyFileWithESModules.js
When I was started with express always wanted a solution to use import instead require
const express = require("express");
// to
import express from "express"
Many time go through this line:- Unfortunately, Node.js doesn't support ES6's import yet.
Now to help other I create new two solutions here
1) esm:-
The brilliantly simple, babel-less, bundle-less ECMAScript module loader.
let's make it work
yarn add esm / npm install esm
create start.js or use your namespace
require = require("esm")(module/*, options*/)
// Import the rest of our application.
module.exports = require('./src/server.js')
// where server.js is express server start file
Change in your package.josn pass path of start.js
"scripts": {
"start": "node start.js",
"start:dev": "nodemon start.js",
},
"dependencies": {
+ "esm": "^3.2.25",
},
"devDependencies": {
+ "nodemon": "^1.19.2"
}
2) Babel js:-
This can be divide into 2 part
a) Solution 1 thanks to timonweb.com
b) Solution 2
use Babel 6 (older version of babel-preset-stage-3 ^6.0)
create .babelrc file at your root folder
{
"presets": ["env", "stage-3"]
}
Install babel-preset-stage-3
yarn add babel-cli babel-polyfill babel-preset-env bable-preset-stage-3 nodemon --dev
Change in package.json
"scripts": {
+ "start:dev": "nodemon --exec babel-node -- ./src/index.js",
+ "start": "npm run build && node ./build/index.js",
+ "build": "npm run clean && babel src -d build -s --source-maps --copy-files",
+ "clean": "rm -rf build && mkdir build"
},
"devDependencies": {
+ "babel-cli": "^6.26.0",
+ "babel-polyfill": "^6.26.0",
+ "babel-preset-env": "^1.7.0",
+ "babel-preset-stage-3": "^6.24.1",
+ "nodemon": "^1.19.4"
},
Start your server
yarn start / npm start
Oooh no we create new problem
regeneratorRuntime.mark(function _callee(email, password) {
^
ReferenceError: regeneratorRuntime is not defined
This error only come when you use async/await in your code.
Then use polyfill that includes a custom regenerator runtime and core-js.
add on top of index.js
import "babel-polyfill"
This allow you to use async/await
use Babel 7
Need to upto date every thing in your project
let start with babel 7
.babelrc
{
"presets": ["#babel/preset-env"]
}
Some change in package.json
"scripts": {
+ "start:dev": "nodemon --exec babel-node -- ./src/index.js",
+ "start": "npm run build && node ./build/index.js",
+ "build": "npm run clean && babel src -d build -s --source-maps --copy-files",
+ "clean": "rm -rf build && mkdir build",
....
}
"devDependencies": {
+ "#babel/cli": "^7.0.0",
+ "#babel/core": "^7.6.4",
+ "#babel/node": "^7.0.0",
+ "#babel/polyfill": "^7.0.0",
+ "#babel/preset-env": "^7.0.0",
+ "nodemon": "^1.19.4"
....
}
and use import "#babel/polyfill" on start point
import "#babel/polyfill"
import express from 'express'
const app = express()
//GET request
app.get('/', async (req, res) {
// await operation
res.send('hello world')
})
app.listen(4000, () => console.log('🚀 Server listening on port 400!'))
Are you thinking why start:dev
Seriously. It is good question if you are new. Every change you are boar with start server every time
then use yarn start:dev as development server every change restart server automatically for more on nodemon
if you can use 'babel', try to add build scripts in package.json(--presets=es2015) as below. it make to precompile import code to es2015
"build": "babel server --out-dir build --presets=es2015 && webpack"
As of Node.js v12 (and this is probably fairly stable now, but still marked "experimental"), you have a couple of options for using ESM (ECMAScript Modules) in Node.js (for files, there's a third way for evaling strings), here's what the documentation 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.
Node.js will treat as CommonJS all other forms of input, such as .js files
where the nearest parent package.json file contains no top-level "type"
field, or string input without the flag --input-type. This behavior is to
preserve backward compatibility. However, now that Node.js supports both
CommonJS and ES modules, it is best to be explicit whenever possible. Node.js
will treat the following as CommonJS when passed to node as the initial input,
or when referenced by import statements within ES module code:
Files ending in .cjs.
Files ending in .js, or extensionless files, when the nearest parent
package.json file contains a top-level field "type" with a value of
"commonjs".
Strings passed in as an argument to --eval or --print, or piped to
node via STDIN, with the flag --input-type=commonjs.
I'm going to address another problem within the original question that no one else has. After recently converting from CommonJS to ESM in my own NodeJS project, I've seen very little discussion about the fact that you cannot place imports wherever you want, like you could with require. My project is working great with imports now, but when I use the code in the question, I first get an error for not having a named function. After naming the function, I receive the following...
import express from 'express'
^^^^^^^
SyntaxError: Unexpected identifier
at Loader.moduleStrategy (internal/modules/esm/translators.js:88:18)
You cannot place imports inside functions like you could require. They have to be placed at the top of the file, outside code blocks. I wasted quite a bit of time on this issue myself.
So while all of the above answers are great at helping you get imports to work in your project, none address the fact that the code in the original question cannot work as written.
import statements are supported in the stable release of Node since version 14.x LTS.
All you need to do is specify "type": "module" in package.json.
In my case it was looking after .babelrc file, and it should contain something like this:
{
"presets": ["es2015-node5", "stage-3"],
"plugins": []
}
My project uses node v10.21.0, which still does not support ES6 import keyword. There are multiple ways to make node recognize import, one of them is to start node with node --experimental-modules index.mjs (The mjs extension is already covered in one of the answers here). But, this way, you will not be able to use node specific keyword like require in your code. If there is need to use both nodejs's require keyword along with ES6's import, then the way out is to use the esm npm package. After adding esm package as a dependency, node needs to be started with a special configuration like: node -r esm index.js
I've been trying to get this working. Here's what works:
Use a recent node version. I'm using v14.15.5. Verify your version by running: node --version
Name the files so that they all end with .mjs rather than .js
Example:
mod.mjs
export const STR = 'Hello World'
test.mjs
import {STR} from './mod.mjs'
console.log(STR)
Run: node test.mjs
You should see "Hello World".
Simply install a higher version of Node. As till Node v10 es6 is not supported. You need to disable a few flags or use
I don't understand what is wrong.
Node v5.6.0
NPM v3.10.6
The code:
function (exports, require, module, __filename, __dirname) {
import express from 'express'
};
The error:
SyntaxError: Unexpected token import
at exports.runInThisContext (vm.js:53:16)
at Module._compile (module.js:387:25)
at Object.Module._extensions..js (module.js:422:10)
at Module.load (module.js:357:32)
at Function.Module._load (module.js:314:12)
at Function.Module.runMain (module.js:447:10)
at startup (node.js:140:18)
at node.js:1001:3
Node 13+ Since Node 13, you can use either the .mjs extension, or set {"type": "module"} in your package.json. You don't need to use the --experimental-modules flag. Modules is now marked as stable in node.js
Node 12 Since Node 12, you can use either the .mjs extension, or set "type": "module" in your package.json. And you need to run node with the --experimental-modules flag.
Node 9 In Node 9, it is enabled behind a flag, and uses the .mjs extension.
node --experimental-modules my-app.mjs
While import is indeed part of ES6, it is unfortunately not yet supported in NodeJS by default, and has only very recently landed support in browsers.
See browser compat table on MDN and this Node issue.
From James M Snell's Update on ES6 Modules in Node.js (February 2017):
Work is in progress but it is going to take some time — We’re currently looking at around a year at least.
Until support shows up natively (now marked stable in Node 13+), you'll have to continue using classic require statements:
const express = require("express");
If you really want to use new ES6/7 features in NodeJS, you can compile it using Babel. Here's an example server.
Unfortunately, Node.js doesn't support ES6's import yet.
To accomplish what you're trying to do (import the Express module), this code should suffice
var express = require("express");
Also, be sure you have Express installed by running
$ npm install express
See the Node.js Docs for more information about learning Node.js.
I'm shocked esm hasn't been mentioned. This small, but mighty package allows you to use either import or require.
Install esm in your project
$ npm install --save esm
Update your Node Start Script to use esm
node -r esm app.js
esm just works. I wasted a TON of time with .mjs and --experimental-modules only to find out a .mjs file cannot import a file that uses require or module.exports. This was a huge problem, whereas esm allows you to mix and match and it just figures it out... esm just works.
As mentioned in other answers Node JS currently doesn't support ES6 imports.
(As of now, read EDIT 2)
Enable ES6 imports in node js provides a solution to this issue. I have tried this and it worked for me.
Run the command:
npm install babel-register babel-preset-env --save-dev
Now you need to create a new file (config.js) and add the following code to it.
require('babel-register')({
presets: [ 'env' ]
})
// Import the rest of our application.
module.exports = require('./your_server_file.js')
Now you can write import statements without getting any errors.
Hope this helps.
EDIT:
You need to run the new file which you created with above code. In my case it was config.js. So I have to run:
node config.js
EDIT 2:
While experimenting, I found one easy solution to this issue.
Create .babelrc file in the root of your project.
Add following (and any other babel presets you need, can be added in this file):
{
"presets": ["env"]
}
Install babel-preset-env using command npm install babel-preset-env --save, and then install babel-cli using command npm install babel-cli -g --save
Now, go to the folder where your server or index file exists and run using:
babel-node fileName.js
Or you can run using npm start by adding following code to your package.json file:
"scripts": {
"start": "babel-node src/index.js"
}
Error: SyntaxError: Unexpected token import or SyntaxError: Unexpected token export
Solution: Change all your imports as example
const express = require('express');
const webpack = require('webpack');
const path = require('path');
const config = require('../webpack.config.dev');
const open = require('open');
And also change your export default = foo; to module.exports = foo;
In case that you still can't use "import" here is how I handled it:
Just translate it to a node friendly require. Example:
import { parse } from 'node-html-parser';
Is the same as:
const parse = require('node-html-parser').parse;
babel 7 proposal
can you add dev dependencies
npm i -D #babel/core #babel/preset-env #babel/register
and add a .babelrc in the root
{
"presets": [
[
"#babel/preset-env",
{
"targets": {
"node": "current"
}
}
]
]
}
and add to the .js file
require("#babel/register")
or if you run it in the cli, you could use the require hook as -r #babel/register, ex.
$node -r #babel/register executeMyFileWithESModules.js
When I was started with express always wanted a solution to use import instead require
const express = require("express");
// to
import express from "express"
Many time go through this line:- Unfortunately, Node.js doesn't support ES6's import yet.
Now to help other I create new two solutions here
1) esm:-
The brilliantly simple, babel-less, bundle-less ECMAScript module loader.
let's make it work
yarn add esm / npm install esm
create start.js or use your namespace
require = require("esm")(module/*, options*/)
// Import the rest of our application.
module.exports = require('./src/server.js')
// where server.js is express server start file
Change in your package.josn pass path of start.js
"scripts": {
"start": "node start.js",
"start:dev": "nodemon start.js",
},
"dependencies": {
+ "esm": "^3.2.25",
},
"devDependencies": {
+ "nodemon": "^1.19.2"
}
2) Babel js:-
This can be divide into 2 part
a) Solution 1 thanks to timonweb.com
b) Solution 2
use Babel 6 (older version of babel-preset-stage-3 ^6.0)
create .babelrc file at your root folder
{
"presets": ["env", "stage-3"]
}
Install babel-preset-stage-3
yarn add babel-cli babel-polyfill babel-preset-env bable-preset-stage-3 nodemon --dev
Change in package.json
"scripts": {
+ "start:dev": "nodemon --exec babel-node -- ./src/index.js",
+ "start": "npm run build && node ./build/index.js",
+ "build": "npm run clean && babel src -d build -s --source-maps --copy-files",
+ "clean": "rm -rf build && mkdir build"
},
"devDependencies": {
+ "babel-cli": "^6.26.0",
+ "babel-polyfill": "^6.26.0",
+ "babel-preset-env": "^1.7.0",
+ "babel-preset-stage-3": "^6.24.1",
+ "nodemon": "^1.19.4"
},
Start your server
yarn start / npm start
Oooh no we create new problem
regeneratorRuntime.mark(function _callee(email, password) {
^
ReferenceError: regeneratorRuntime is not defined
This error only come when you use async/await in your code.
Then use polyfill that includes a custom regenerator runtime and core-js.
add on top of index.js
import "babel-polyfill"
This allow you to use async/await
use Babel 7
Need to upto date every thing in your project
let start with babel 7
.babelrc
{
"presets": ["#babel/preset-env"]
}
Some change in package.json
"scripts": {
+ "start:dev": "nodemon --exec babel-node -- ./src/index.js",
+ "start": "npm run build && node ./build/index.js",
+ "build": "npm run clean && babel src -d build -s --source-maps --copy-files",
+ "clean": "rm -rf build && mkdir build",
....
}
"devDependencies": {
+ "#babel/cli": "^7.0.0",
+ "#babel/core": "^7.6.4",
+ "#babel/node": "^7.0.0",
+ "#babel/polyfill": "^7.0.0",
+ "#babel/preset-env": "^7.0.0",
+ "nodemon": "^1.19.4"
....
}
and use import "#babel/polyfill" on start point
import "#babel/polyfill"
import express from 'express'
const app = express()
//GET request
app.get('/', async (req, res) {
// await operation
res.send('hello world')
})
app.listen(4000, () => console.log('🚀 Server listening on port 400!'))
Are you thinking why start:dev
Seriously. It is good question if you are new. Every change you are boar with start server every time
then use yarn start:dev as development server every change restart server automatically for more on nodemon
if you can use 'babel', try to add build scripts in package.json(--presets=es2015) as below. it make to precompile import code to es2015
"build": "babel server --out-dir build --presets=es2015 && webpack"
As of Node.js v12 (and this is probably fairly stable now, but still marked "experimental"), you have a couple of options for using ESM (ECMAScript Modules) in Node.js (for files, there's a third way for evaling strings), here's what the documentation 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.
Node.js will treat as CommonJS all other forms of input, such as .js files
where the nearest parent package.json file contains no top-level "type"
field, or string input without the flag --input-type. This behavior is to
preserve backward compatibility. However, now that Node.js supports both
CommonJS and ES modules, it is best to be explicit whenever possible. Node.js
will treat the following as CommonJS when passed to node as the initial input,
or when referenced by import statements within ES module code:
Files ending in .cjs.
Files ending in .js, or extensionless files, when the nearest parent
package.json file contains a top-level field "type" with a value of
"commonjs".
Strings passed in as an argument to --eval or --print, or piped to
node via STDIN, with the flag --input-type=commonjs.
I'm going to address another problem within the original question that no one else has. After recently converting from CommonJS to ESM in my own NodeJS project, I've seen very little discussion about the fact that you cannot place imports wherever you want, like you could with require. My project is working great with imports now, but when I use the code in the question, I first get an error for not having a named function. After naming the function, I receive the following...
import express from 'express'
^^^^^^^
SyntaxError: Unexpected identifier
at Loader.moduleStrategy (internal/modules/esm/translators.js:88:18)
You cannot place imports inside functions like you could require. They have to be placed at the top of the file, outside code blocks. I wasted quite a bit of time on this issue myself.
So while all of the above answers are great at helping you get imports to work in your project, none address the fact that the code in the original question cannot work as written.
import statements are supported in the stable release of Node since version 14.x LTS.
All you need to do is specify "type": "module" in package.json.
In my case it was looking after .babelrc file, and it should contain something like this:
{
"presets": ["es2015-node5", "stage-3"],
"plugins": []
}
My project uses node v10.21.0, which still does not support ES6 import keyword. There are multiple ways to make node recognize import, one of them is to start node with node --experimental-modules index.mjs (The mjs extension is already covered in one of the answers here). But, this way, you will not be able to use node specific keyword like require in your code. If there is need to use both nodejs's require keyword along with ES6's import, then the way out is to use the esm npm package. After adding esm package as a dependency, node needs to be started with a special configuration like: node -r esm index.js
I've been trying to get this working. Here's what works:
Use a recent node version. I'm using v14.15.5. Verify your version by running: node --version
Name the files so that they all end with .mjs rather than .js
Example:
mod.mjs
export const STR = 'Hello World'
test.mjs
import {STR} from './mod.mjs'
console.log(STR)
Run: node test.mjs
You should see "Hello World".
Simply install a higher version of Node. As till Node v10 es6 is not supported. You need to disable a few flags or use
I don't understand what is wrong.
Node v5.6.0
NPM v3.10.6
The code:
function (exports, require, module, __filename, __dirname) {
import express from 'express'
};
The error:
SyntaxError: Unexpected token import
at exports.runInThisContext (vm.js:53:16)
at Module._compile (module.js:387:25)
at Object.Module._extensions..js (module.js:422:10)
at Module.load (module.js:357:32)
at Function.Module._load (module.js:314:12)
at Function.Module.runMain (module.js:447:10)
at startup (node.js:140:18)
at node.js:1001:3
Node 13+ Since Node 13, you can use either the .mjs extension, or set {"type": "module"} in your package.json. You don't need to use the --experimental-modules flag. Modules is now marked as stable in node.js
Node 12 Since Node 12, you can use either the .mjs extension, or set "type": "module" in your package.json. And you need to run node with the --experimental-modules flag.
Node 9 In Node 9, it is enabled behind a flag, and uses the .mjs extension.
node --experimental-modules my-app.mjs
While import is indeed part of ES6, it is unfortunately not yet supported in NodeJS by default, and has only very recently landed support in browsers.
See browser compat table on MDN and this Node issue.
From James M Snell's Update on ES6 Modules in Node.js (February 2017):
Work is in progress but it is going to take some time — We’re currently looking at around a year at least.
Until support shows up natively (now marked stable in Node 13+), you'll have to continue using classic require statements:
const express = require("express");
If you really want to use new ES6/7 features in NodeJS, you can compile it using Babel. Here's an example server.
Unfortunately, Node.js doesn't support ES6's import yet.
To accomplish what you're trying to do (import the Express module), this code should suffice
var express = require("express");
Also, be sure you have Express installed by running
$ npm install express
See the Node.js Docs for more information about learning Node.js.
I'm shocked esm hasn't been mentioned. This small, but mighty package allows you to use either import or require.
Install esm in your project
$ npm install --save esm
Update your Node Start Script to use esm
node -r esm app.js
esm just works. I wasted a TON of time with .mjs and --experimental-modules only to find out a .mjs file cannot import a file that uses require or module.exports. This was a huge problem, whereas esm allows you to mix and match and it just figures it out... esm just works.
As mentioned in other answers Node JS currently doesn't support ES6 imports.
(As of now, read EDIT 2)
Enable ES6 imports in node js provides a solution to this issue. I have tried this and it worked for me.
Run the command:
npm install babel-register babel-preset-env --save-dev
Now you need to create a new file (config.js) and add the following code to it.
require('babel-register')({
presets: [ 'env' ]
})
// Import the rest of our application.
module.exports = require('./your_server_file.js')
Now you can write import statements without getting any errors.
Hope this helps.
EDIT:
You need to run the new file which you created with above code. In my case it was config.js. So I have to run:
node config.js
EDIT 2:
While experimenting, I found one easy solution to this issue.
Create .babelrc file in the root of your project.
Add following (and any other babel presets you need, can be added in this file):
{
"presets": ["env"]
}
Install babel-preset-env using command npm install babel-preset-env --save, and then install babel-cli using command npm install babel-cli -g --save
Now, go to the folder where your server or index file exists and run using:
babel-node fileName.js
Or you can run using npm start by adding following code to your package.json file:
"scripts": {
"start": "babel-node src/index.js"
}
Error: SyntaxError: Unexpected token import or SyntaxError: Unexpected token export
Solution: Change all your imports as example
const express = require('express');
const webpack = require('webpack');
const path = require('path');
const config = require('../webpack.config.dev');
const open = require('open');
And also change your export default = foo; to module.exports = foo;
In case that you still can't use "import" here is how I handled it:
Just translate it to a node friendly require. Example:
import { parse } from 'node-html-parser';
Is the same as:
const parse = require('node-html-parser').parse;
babel 7 proposal
can you add dev dependencies
npm i -D #babel/core #babel/preset-env #babel/register
and add a .babelrc in the root
{
"presets": [
[
"#babel/preset-env",
{
"targets": {
"node": "current"
}
}
]
]
}
and add to the .js file
require("#babel/register")
or if you run it in the cli, you could use the require hook as -r #babel/register, ex.
$node -r #babel/register executeMyFileWithESModules.js
When I was started with express always wanted a solution to use import instead require
const express = require("express");
// to
import express from "express"
Many time go through this line:- Unfortunately, Node.js doesn't support ES6's import yet.
Now to help other I create new two solutions here
1) esm:-
The brilliantly simple, babel-less, bundle-less ECMAScript module loader.
let's make it work
yarn add esm / npm install esm
create start.js or use your namespace
require = require("esm")(module/*, options*/)
// Import the rest of our application.
module.exports = require('./src/server.js')
// where server.js is express server start file
Change in your package.josn pass path of start.js
"scripts": {
"start": "node start.js",
"start:dev": "nodemon start.js",
},
"dependencies": {
+ "esm": "^3.2.25",
},
"devDependencies": {
+ "nodemon": "^1.19.2"
}
2) Babel js:-
This can be divide into 2 part
a) Solution 1 thanks to timonweb.com
b) Solution 2
use Babel 6 (older version of babel-preset-stage-3 ^6.0)
create .babelrc file at your root folder
{
"presets": ["env", "stage-3"]
}
Install babel-preset-stage-3
yarn add babel-cli babel-polyfill babel-preset-env bable-preset-stage-3 nodemon --dev
Change in package.json
"scripts": {
+ "start:dev": "nodemon --exec babel-node -- ./src/index.js",
+ "start": "npm run build && node ./build/index.js",
+ "build": "npm run clean && babel src -d build -s --source-maps --copy-files",
+ "clean": "rm -rf build && mkdir build"
},
"devDependencies": {
+ "babel-cli": "^6.26.0",
+ "babel-polyfill": "^6.26.0",
+ "babel-preset-env": "^1.7.0",
+ "babel-preset-stage-3": "^6.24.1",
+ "nodemon": "^1.19.4"
},
Start your server
yarn start / npm start
Oooh no we create new problem
regeneratorRuntime.mark(function _callee(email, password) {
^
ReferenceError: regeneratorRuntime is not defined
This error only come when you use async/await in your code.
Then use polyfill that includes a custom regenerator runtime and core-js.
add on top of index.js
import "babel-polyfill"
This allow you to use async/await
use Babel 7
Need to upto date every thing in your project
let start with babel 7
.babelrc
{
"presets": ["#babel/preset-env"]
}
Some change in package.json
"scripts": {
+ "start:dev": "nodemon --exec babel-node -- ./src/index.js",
+ "start": "npm run build && node ./build/index.js",
+ "build": "npm run clean && babel src -d build -s --source-maps --copy-files",
+ "clean": "rm -rf build && mkdir build",
....
}
"devDependencies": {
+ "#babel/cli": "^7.0.0",
+ "#babel/core": "^7.6.4",
+ "#babel/node": "^7.0.0",
+ "#babel/polyfill": "^7.0.0",
+ "#babel/preset-env": "^7.0.0",
+ "nodemon": "^1.19.4"
....
}
and use import "#babel/polyfill" on start point
import "#babel/polyfill"
import express from 'express'
const app = express()
//GET request
app.get('/', async (req, res) {
// await operation
res.send('hello world')
})
app.listen(4000, () => console.log('🚀 Server listening on port 400!'))
Are you thinking why start:dev
Seriously. It is good question if you are new. Every change you are boar with start server every time
then use yarn start:dev as development server every change restart server automatically for more on nodemon
if you can use 'babel', try to add build scripts in package.json(--presets=es2015) as below. it make to precompile import code to es2015
"build": "babel server --out-dir build --presets=es2015 && webpack"
As of Node.js v12 (and this is probably fairly stable now, but still marked "experimental"), you have a couple of options for using ESM (ECMAScript Modules) in Node.js (for files, there's a third way for evaling strings), here's what the documentation 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.
Node.js will treat as CommonJS all other forms of input, such as .js files
where the nearest parent package.json file contains no top-level "type"
field, or string input without the flag --input-type. This behavior is to
preserve backward compatibility. However, now that Node.js supports both
CommonJS and ES modules, it is best to be explicit whenever possible. Node.js
will treat the following as CommonJS when passed to node as the initial input,
or when referenced by import statements within ES module code:
Files ending in .cjs.
Files ending in .js, or extensionless files, when the nearest parent
package.json file contains a top-level field "type" with a value of
"commonjs".
Strings passed in as an argument to --eval or --print, or piped to
node via STDIN, with the flag --input-type=commonjs.
I'm going to address another problem within the original question that no one else has. After recently converting from CommonJS to ESM in my own NodeJS project, I've seen very little discussion about the fact that you cannot place imports wherever you want, like you could with require. My project is working great with imports now, but when I use the code in the question, I first get an error for not having a named function. After naming the function, I receive the following...
import express from 'express'
^^^^^^^
SyntaxError: Unexpected identifier
at Loader.moduleStrategy (internal/modules/esm/translators.js:88:18)
You cannot place imports inside functions like you could require. They have to be placed at the top of the file, outside code blocks. I wasted quite a bit of time on this issue myself.
So while all of the above answers are great at helping you get imports to work in your project, none address the fact that the code in the original question cannot work as written.
import statements are supported in the stable release of Node since version 14.x LTS.
All you need to do is specify "type": "module" in package.json.
In my case it was looking after .babelrc file, and it should contain something like this:
{
"presets": ["es2015-node5", "stage-3"],
"plugins": []
}
My project uses node v10.21.0, which still does not support ES6 import keyword. There are multiple ways to make node recognize import, one of them is to start node with node --experimental-modules index.mjs (The mjs extension is already covered in one of the answers here). But, this way, you will not be able to use node specific keyword like require in your code. If there is need to use both nodejs's require keyword along with ES6's import, then the way out is to use the esm npm package. After adding esm package as a dependency, node needs to be started with a special configuration like: node -r esm index.js
I've been trying to get this working. Here's what works:
Use a recent node version. I'm using v14.15.5. Verify your version by running: node --version
Name the files so that they all end with .mjs rather than .js
Example:
mod.mjs
export const STR = 'Hello World'
test.mjs
import {STR} from './mod.mjs'
console.log(STR)
Run: node test.mjs
You should see "Hello World".
Simply install a higher version of Node. As till Node v10 es6 is not supported. You need to disable a few flags or use