ChatGPT解决这个技术问题 Extra ChatGPT

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",
Hi, having the same problem right now. Could you also share your dependencies? Maybe even a diff before and after your update. I could check against mine to see if we can find similar packages which might cause the trouble.
I just replaced all the "imports" with "requires" and all is well now. Dumb but it wasn't worth the effort to figure it out right now. I will update the original with dependencies, though. If you get any leads, I'll check them out against my original code.
CommonJS syntax (require and module.exports) was the original format for node and webpack also supports it, but ES6 module syntax (export, import) is the newer way and now node and webpack support it. I read that node supports import now but so many tutorials show require for pure node stuff that it's likely better to use that syntax for node.
Hm, interesting, that preset only sets the {allowJs: true} setting. Same I also (already) added to the TS compilerOptions. Maybe you want to have a look into this. edit: omg, in case you actually use TS? ... what a config hell.
"type":"module" doesn't solve my problem, and there are over a hundred of imports. Syntax of require is diff from imports, not an easy replace. Can you give an example of how imports is replaced by requires?

P
Peter Mortensen

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 I use this, then change the path to include the "js" for the required file, then change the format of the export statements in the required file, and then take all the "require" statements I changed from "import"—because now "require" is unknown—this will work, so I'll accept this answer.
This is not really an option if the problem is under node_modules/ right? Any ideas how to fix in that case?
or use babel! ` module.exports = { presets: ['@babel/preset-env'], }; `
@Cocuba answer is spot on and should be the accepted answer because it actually transpiles.
This solution doesn't work if you're running .ts files. If you could add that simply using nodemon instead of node, as per this answer stackoverflow.com/a/65058291/11664580 down below, it would hopefully save people the half a day I've spent messing around. Alternatively, installing ts-node seems to be a solution, as per stackoverflow.com/a/61947868/11664580
P
Peter Mortensen

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.


If you're using babel-node, then you'll also need to use the --extensions option, e.g. babel-node --extensions \".ts,.tsx\" src/index
Yep, this did it where as trying "type" : "module" made it all of the sudden say "require is undefined".
Damn it saved me from lots of trouble. I did the same mistake coming under the impressino that esnext is the best
your answer works. could you explain why should we tweak like this? @Dr-Bracket Thank you
Simple and resolved the issue for me.
B
Brian Burns

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": { ...
  },
  ...
}

tx, but do you have an idea where I can find the package.json?? I am using netbeans. I also searched for package.json on my macbook but I see a lot of package.json files. Any tips?
Hi Alex, it's been a while since worked in Java project but I hope that this link can give you a clue on where to locate the package.json file: stackoverflow.com/questions/41513559/…
L
Liam

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


2020 update: --experimental-modules is no longer required.
Not saying this answer is wrong, I've seen the same docs. But I don't see how the suggestion to use import() to access es6 module in CommonJS is useful. It's async and so can't be used to import anything at the file level. Which makes trying to access es6 modules from CommonJS painful to say the least. Considering that the main unit test frameworks Jasmine Jest etc don't handle this at all well it leaves me thinking that until there is better interop support the whole Node es6 situation seems half baked to me, but I'd love to be proven wrong.
P
Peter Mortensen

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


P
Peter Mortensen

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


A
Alisson Reinaldo Silva

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"
  }
}

I had the same issue. As an alternative, simply running the package.json script using nodemon instead of node works too. Saves the need for installing another package (assuming you're already running nodemon). credit: stackoverflow.com/a/65058291/11664580
Yes, this saved me! Thanks!
They should go to devDependencies instead.
P
Peter Mortensen

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

A
Abhishek Kumar

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

+1 esm seems to be the easiest solution when you cannot add "type": "module" to the package.json file.
A
Adrian

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);
});

D
David S

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 found this answer the most clear explanation to OP. Just that, say I'm writing an app, not a module, does "Cannot use import statement outside a module" means that I cannot use the import statement to import anything, since I'm outside a module, right? This is still confusing. For "Files including node modules must either end in .mjs or the nearest package.json file must contain "type": "module".", I'm writing an app, not a module, why I need to name my app with mjs or set my package to module?
@xpt Hey. So, you can't compare an app and a module. I think you maybe be thinking of it in terms of node modules which seems like a program within your program. This isn't really what a module is. Let me clarify what a module is and I think that'll solve your confusion:
@xpt Think of it this way, you're writing an app and working on a file named main-file.js. You want to import a function from another file called some-other-file.js. some-other-file.js is quite large and you don't need the entire file. You just want a function from the file. Now if some-other-file.js and main-file.js were modules (.mjs), you could 'import' the function you so desire e.g. import someFunction from './some-other-file'. To sum it up, a module is a js file that can be separated by its functions so it can export particular functions opposed to the whole file. Does that make sense?
Thanks for the explanation David. So I understand some-other-file.js is module, which can export particular functions opposed to the whole file. However, is main-file.js a module too? No, it's only my main of my app. Would the "Cannot use import statement outside a module" rule apply to main-file.js (since it is not a module)?
Anyway, I think I'd better ask a new question instead -- stackoverflow.com/questions/71240736
V
Vidya Sagar H J

To use import, do one of the following.

Rename the .js file to .mjs In package.json file, add {type:module}


this works without adding {type:module} in package.json
P
Peter Mortensen

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!


Perhaps nodemon executes files as modules, so intrinsically error disappears
P
Peter Mortensen

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.


D
Daniel

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!

https://i.stack.imgur.com/4SsC9.png

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

https://i.stack.imgur.com/vCXPq.png

the full information is here; https://babeljs.io/docs/en/babel-node


F
Faisal Amin

in the package.json write { "type": "module" }

it fixed my problem, I had the same problem


the same answer was given above and got many upvote.
A
Ahmed Adewale

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


P
Peter Mortensen

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'],
};

P
Peter Mortensen

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'

L
Luca C.

if you are using ES6 JS 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 npm command, next in package.json you change your npm command to enable experimental ES6 support for jest, and configure jest to do it


P
Peter Mortensen

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).


P
Peter Mortensen

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


P
Peter Mortensen

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

this flag seems to have been removed from latest versions
P
Peter Mortensen

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".


n
ncutixavier

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

this did not work for me
P
Pieterjan

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',
},

E
Ekansh Saxena

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


D
DariusV

https://i.stack.imgur.com/omFRZ.png

be aware you must install babel and babel register


h
halfer

I had this problem in a fledgling Express API project.

The offending server code in src/server/server.js:

import express from 'express';
import {initialDonationItems, initialExpenditureItems} from "./DemoData";

const server = express();

server.get('/api/expenditures', (req, res) => {
  res.type('json');
  res.send(initialExpenditureItems);
});

server.get('/api/donations', (req, res) => {
  res.type('json');
  res.send(initialDonationItems);
});

server.listen(4242, () => console.log('Server is running...'));

Here were my dependencies:

{
  "name": "contributor-api",
  "version": "0.0.1",
  "description": "A Node backend to provide storage services",
  "scripts": {
    "dev-server": "nodemon --exec babel-node src/server/server.js --ignore dist/",
    "test": "jest tests"
  },
  "license": "ISC",
  "dependencies": {
    "@babel/core": "^7.9.6",
    "@babel/node": "^7.8.7",
    "babel-loader": "^8.1.0",
    "express": "^4.17.1",
    "mysql2": "^2.1.0",
    "sequelize": "^5.21.7",
    "sequelize-cli": "^5.5.1"
  },
  "devDependencies": {
    "jest": "^25.5.4",
    "nodemon": "^2.0.3"
  }
}

And here was the runner that threw the error:

nodemon --exec babel-node src/server/server.js --ignore dist

This was frustrating, as I had a similar Express project that worked fine.

The solution was firstly to add this dependency:

npm install @babel/preset-env

And then to wire it in using a babel.config.js in the project root:

module.exports = {
  presets: ['@babel/preset-env'],
};

I don't fully grok why this works, but I copied it from an authoritative source, so I am happy to stick with it.


Yeah, my issue was that the code had a bunch of presets and I could never quite hit the balance right of things I wanted vs. things I didn't want/that broke stuff.
I've been pushing through confusing JS crashes all day @user3810626 - I suspect my problem is that I'm quite new to the language and the ecosystem, and I need to put some learning aside for now to get stuff working. Getting there... :-)
Good luck! It's a jungle out there! (I mean, literally, the JS ecosystem is a jungle...)
@user3810626 nodejs devs dont know how things work anymore. they just keep trying Stack Overflow solutions until something sticks
This seems to be truer in some communities than others.
P
PositiveGuy

Taking out "module": "esnext" and making sure "moduleResolution": "node" is in it, that specific combo did it for me