SyntaxError: Cannot use import statement outside a module

Question

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",

Woodson

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. – Meli

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. – Woodson

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. – Edgardoedge

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. – Meli

I used a package called package called esm to write the code in es6. npmjs.com/package/esm – Oppenheimer

Please refer to my answer here https://mcmap.net/q/67944/-how-to-resolve-quot-cannot-use-import-statement-outside-a-module-quot-from-jest-when-running-tests – Mudslinger

"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? – Briony

The Powers That Be: A (mildly) comic way of saying "I don't know where this is being decided." – Woodson

Something seems to be missing at the end (after "babel-preset-es2015": "^6.24.1",). Can you make it clearer? Either why nothing is actually missing or adding the missing part (including "}"). – Lysenkoism

I cannot, alas. I remember the issue, and I remember getting around it in a really cheesy way, but I do not think I can recreate it now. – Woodson

I had the same issue the last couple of days ... not a type:module issue ... not a config issue ... the issue was coming from the : cluster.fork(). (npm cluster module) I have no problem with the "master" instance but the children were "broken". as I'm in a dev environement... I don't care about clustring. – Pansypant

Answer 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.

Elisabeth

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. – Woodson

This is not really an option if the problem is under node_modules/ right? Any ideas how to fix in that case? – Coeternal

or use babel! ` module.exports = { presets: ['@babel/preset-env'], }; ` – Inamorato

I'm at node 14.9.0, VSC, added "type":"module" solved express. But now did you mean to import env.js for import env from './env' Seems like I have to edit every file? – Briony

@Inamorato answer is spot on and should be the accepted answer because it actually transpiles. – Alphabetic

Yes this works fine to my case that trying to import React module. – Dandelion

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 https://mcmap.net/q/63715/-syntaxerror-cannot-use-import-statement-outside-a-module 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 https://mcmap.net/q/63715/-syntaxerror-cannot-use-import-statement-outside-a-module – Scarcely

I had a hidden package.json in one of my source directories. Had to do a find . -name package.json and my imports started working. – Atc

Adding "type": "module" isn't solving the error for me. – Sorcha

I like the additional note about the .cjs extension. Very useful. – Lots

my package.json file dont have a { "type":"module" } it have { "dependencies": { "chalk": "^4.1.2", "discord.js": "^14.6.0", "express": "^4.18.2", "pureimage": "^0.3.14" } } – Dulse

But when I add type: module, if I use require, I'll get an error: ReferenceError: require is not defined in ES module scope, you can use import instead – Emera

It breaks eslint. [eslint] Cannot read config file – Impacted

Answer 2

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.

Delagarza

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 – Joe

Yep, this did it where as trying "type" : "module" made it all of the sudden say "require is undefined". – Angelangela

Damn it saved me from lots of trouble. I did the same mistake coming under the impressino that esnext is the best – Dielu

your answer works. could you explain why should we tweak like this? @Delagarza Thank you – Diablerie

Simple and resolved the issue for me. – Madewell

This has resolved the issue for me. Thanks. Could you please elaborate on why esnext was not the best option? – Babushka

esnext is a false friend! – Gownsman

Could you elaborate more, lol. – Dedradedric

Answer 3

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

Anselme

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? – Kearney

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: #41514059 – Anselme

But when I add type: module, if I use require, I'll get an error: ReferenceError: require is not defined in ES module scope, you can use import instead – Emera

Answer 4

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

Dronski

2020 update: --experimental-modules is no longer required. – Prevalent

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. – Aniakudo

add it where? Can we get a code example please. – Ser

adding it breaks my 'require's ReferenceError: require is not defined – Ser

@johnktejik use createRequire to define a function in an ESM file that works like require() does in CommonJS files. (The opposite way around—CJS in ESM—is simply const foo = await import('./some-module.js')) – Bernardinabernardine

But when I add type: module, if I use require, I'll get an error: ReferenceError: require is not defined in ES module scope, you can use import instead – Emera

See this answer for a code example using import(). – Cartierbresson

Answer 5

I ran into the same issue and it's even worse: I needed both "import" and "require"

1. Some newer ES6 modules works only with import.
2. Some CommonJS works with require.

Here is what worked for me:

1. Turn your js file into .mjs as suggested in other answers

2. "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.

3. 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

Palpable

Reading the Node.js documentation, import will handle both ES and CommonJS modules; require only handles CommonJS modules. nodejs.org/api/esm.html#import-expressions – Schriever

Answer 6

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

Shaylynn

Answer 7

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

Spoonfeed

does this work with nodemon hot reloading in development? – Sloan

Answer 8

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"
  }
}

Integrate

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: https://mcmap.net/q/63715/-syntaxerror-cannot-use-import-statement-outside-a-module – Scarcely

They should go to devDependencies instead. – Female

Answer 9

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

Rempe

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

This should be the accepted answer. esm solves the issue. Thank you. For anyone trying to import express or any other module into your Express application instead of doing a require, this is ideal. – Travis

Answer 10

Node.js 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);
});

Coherence

this worked for me. Wtf is up with node-fetch? – Karmenkarna

I usually don't mind "solving the problem" a different way but using a different library that doesn't have the same module semantics seems like last-resort and didn't really solve or understand the original problem which is what this question is about. – Coax

Answer 11

If you are using ES6 JavaScript imports:

1. install cross-env
2. in package.json change "test": "jest" to "test": "cross-env NODE_OPTIONS=--experimental-vm-modules jest"
3. 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.

Indefectible

Answer 12

I found the 2020 update to this answer helpful to answering this question as well as telling you why it does this:

Here's an excerpt:

Since Node.js v12 (April 2019), support for ES modules is enabled by default, and since Node.js v15 (October 2020) it's stable (see here). Files, including Node.js modules, must either end in .mjs or the nearest package.json file must contain "type": "module". The Node.js documentation has a ton more information, also about interoperability between CommonJS and ES modules.

Hekate

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? – Estabrook

@Estabrook 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: – Hekate

@Estabrook 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? – Hekate

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)? – Estabrook

Anyway, I think I'd better ask a new question instead -- stackoverflow.com/questions/71240736 – Estabrook

Related: What do we do with answers that are entirely copied and improperly attributed (only a "reference" link or similar is included)? – Lysenkoism

Answer 13

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) => { }"

Erikaerikson

Answer 14

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!

The problem is that node does not accept TypeScript files. Instead, ts-node might be the perfect replacement.

Sukkah

Perhaps nodemon executes files as modules, so intrinsically error disappears – Sloven

Answer 15

To use import, do one of the following.

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

Adios

this works without adding {type:module} in package.json – Mowry

Lol, since when the Nodejs files must be named ".mjs" instead of ".js". Weird, but it worked for me – Eyrie

Answer 16

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.

Menial

Answer 17

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',
},

Deaf

That works for me. Thks. But now i'm giving this error The injectable 'PlatformLocation' needs to be compiled using the JIT compiler, but '@angular/compiler' is not available – Club

Answer 18

If you want to use Babel, I have a simple solution for that!

Remember this is for Node.js example: like an Express.js 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

Then configure your Babel file in your repository!

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 on @babel/node.

Waxwork

What is "WAO"? – Lysenkoism

Answer 19

If you are using the Vite - React application with the Speedy Web Compiler (SWC) and you tried to import the various methods of the Jest testing library ({import { describe, expect, test } from "@jest/globals";), all your tests will run individually and outside the module. Hence you might get the error as:

SyntaxError: Cannot use import statement outside a module

Since you are using SWC, the Babel configuration won't help. So it could be resolved by just giving a simple development dependency:

npm install --save-dev @types/jest

Later remove the import statement, use methods (describe, test, expect, afterAll, afterEach, beforeAll, beforeEach, fail, fdescribe, fit, it, jasmine, jest, pending, spyOn, xdescribe, xit, xtest) directly since there are treated as globals. Install the link and other documentation here! @types/jest

Test your sum.test.js by npm run test, supposing you have"test": "jest" in scripts commands and jest in dev dependency:

const sum = (val1, val2) => {
  return val1 + val2;
};

describe("sum module", () => {
  test("adds 1 + 2 to equal 3", () => {
    expect(sum(1, 2)).toBe(3);
  });
});

Lancastrian

Answer 20

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'],
};

Radom

Answer 21

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'

Balanchine

Answer 22

I had this issue when I was running a migration.

It's an 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.

Babette

What do you mean by ".sequelizerc file my"? Please respond by editing (changing) your answer, not here in comments (but *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** without *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** "Edit:", "Update:", or similar - the answer should appear as if it was written today). – Lysenkoism

Answer 23

For people coming to this question due to this error in Netlify functions even after adding "type": "module" in the package.json file, update your netlify.toml file to use 'esbuild'. Since esbuild supports ES6, it would work.

[functions]
  node_bundler = "esbuild"

Reference: Get started with functions

Manly

Answer 24

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.

Absorptivity

Answer 25

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).

Trochal

Answer 26

1. 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..)
2. 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.
3. 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.
4. Of course, with babel-node, you also normally need and edit another file, such as the babel.config.js/.babelrc file

Excrescent

Answer 27

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

Desinence

this flag seems to have been removed from latest versions – Monogenesis

Answer 28

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".

Georgy

Answer 29

If you are using Node.js, you should refer to this document. Just set up Babel in your Node.js application. It will work, and it worked for me.

npm install --save-dev @babel/cli @babel/core @babel/preset-env

Champ

this did not work for me – Blakemore

Answer 30

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.

Inexcusable

Answer 31

In my case, I used the swc command to transpile, and the problem was the .wscrc file missing. Due to the lack of this file, it was not being transpiled and that is why there is an error.

My solution:

• Transpile command on package.json "dist": "swc src -d dist --source-maps --copy-files",

• .wscrc config file:

{
    "jsc": {
      "parser": {
        "syntax": "typescript",
        "tsx": false,
        "dynamicImport": true,
        "decorators": true
      },
      "transform": {
        "legacyDecorator": true,
        "decoratorMetadata": true
      },
      "target": "es2020",
      "externalHelpers": false,
      "keepClassNames": true,
      "loose": false,
      "minify": {
        "compress": false,
        "mangle": false
      },
      "baseUrl": "src",
      "paths": {
        "@/*": ["*"]
      }
    },
    "module": {
      "type": "commonjs"
    }
  }

Longstanding

Answer 32

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.

Pinhead

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. – Woodson

I've been pushing through confusing JS crashes all day @Woodson - 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... :-) – Pinhead

Good luck! It's a jungle out there! (I mean, literally, the JS ecosystem is a jungle...) – Woodson

@Woodson nodejs devs dont know how things work anymore. they just keep trying Stack Overflow solutions until something sticks – Minaminabe

This seems to be truer in some communities than others. – Woodson

Answer 33

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.

Apology

Please review Why not upload images of code/errors when asking a question? (e.g., "Images should only be used to illustrate problems that can't be made clear in any other way, such as to provide screenshots of a user interface.") and do the right thing (it covers answers as well). Thanks in advance. – Lysenkoism