'ExpressJs is return error `ERR_MODULE_NOT_FOUND` if I import the file without `js` extension

I build a expressJs app by ES6 and I got the below error:

(node:4132) ExperimentalWarning: The ESM module loader is experimental.
internal/modules/run_main.js:54
    internalBinding('errors').triggerUncaughtException(
                              ^

Error [ERR_MODULE_NOT_FOUND]: Cannot find module 'E:\wamp64\www\myDemos\nodeJs\expressJsExample\config\app' imported from E:\wamp64\www\myDemos\nodeJs\expressJsExample\server.mjs
←[90m    at finalizeResolution (internal/modules/esm/resolve.js:255:11)←[39m
←[90m    at moduleResolve (internal/modules/esm/resolve.js:603:10)←[39m
←[90m    at Loader.defaultResolve [as _resolve] (internal/modules/esm/resolve.js:644:13)←[39m
←[90m    at Loader.resolve (internal/modules/esm/loader.js:94:40)←[39m
←[90m    at Loader.getModuleJob (internal/modules/esm/loader.js:240:28)←[39m
←[90m    at ModuleWrap.<anonymous> (internal/modules/esm/module_job.js:42:40)←[39m
←[90m    at link (internal/modules/esm/module_job.js:41:36)←[39m {
  code: ←[32m'ERR_MODULE_NOT_FOUND'←[39m
}
[nodemon] app crashed - waiting for file changes before starting...

If I use import app from './config/app.js'; then working but if I use import app from './config/app'; then return the above error.

The below is my code:

package.json

{
  "name": "ExpressJsExample",
  "version": "1.0.0",
  "description": "Express Js Example",
  "main": "server.js",
  "type": "module",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "nodemon server.js"
  },
  "author": "Mukesh Singh Thakur",
  "license": "ISC",
  "dependencies": {
    "body-parser": "^1.19.0",
    "chalk": "^4.0.0",
    "dotenv": "^8.2.0",
    "express": "^4.17.1",
    "http": "0.0.1-security",
    "http-errors": "^1.7.3",
    "jsonwebtoken": "^8.5.1",
    "nodemon": "^2.0.2",
    "pg": "^8.0.0",
    "request": "^2.88.2",
    "sequelize": "^5.21.6"
  },
  "devDependencies": {
    "sequelize-cli": "^5.5.1"
  }
}

server.js

import http from 'http';
import app from './config/app';

const server = http.Server(app);
server.listen(3000, () => {
       return true;
});

app.js

import express from 'express';
const app = express();

export default app;

The example app is available in https://github.com/msthakur08/express-js-example URL. The example files import with '.js' existence but I want to import file without '.js' existence.

node.jsexpressecmascript-6es6-modules


Solution 1:[1]

You can resolve this by:

Add node --es-module-specifier-resolution=node to your node command.

Full Command : node --experimental-modules --es-module-specifier-resolution=node app.js

Solution 2:[2]

If someone is still searching, I got this error using node version 15, I was importing the files without the .js file extension, adding that fixed my issue.

Solution 3:[3]

You can add this to your package json

"scripts": {
    "start": "nodemon --experimental-modules --es-module-specifier-resolution=node index.js"
},

Solution 4:[4]

I solved this with this approach:-

When You are using Es6 import/export functionality with node, you need to import modules with ".mjs" extensionand before importing rename your module ./path-to/app.js to ./path-to/app.mjs

and change your code to this

import http from 'http';
import app from './config/app.mjs'; //.mjs extension is necessary

const server = http.Server(app);
server.listen(3000, () => {
       return true;
});

and run your app.js with node --experimental-modules app.js

more on this https://nodejs.org/api/esm.html

Solution 5:[5]

I faced the same problem, and it got resolved when i removed the type:"module" from package.json

Solution 6:[6]

As example import 'express' is resolved as ./node_modules/express/index.js.

In your case, create a folder called app with an index.js inside of it. After that you can import or require it using this line:

import app from './app/'

Solution 7:[7]

I resolved this issue by below steps

  1. Install esm library

  2. Removed the type:"module" from package.json

  3. Added below command in package.json

    "scripts": {"start": "nodemon -r esm app/index.js"}

It's working for node 14 version

Solution 8:[8]

try changing the type using common, so import is changed to require

Solution 9:[9]

first of all install nodmodule :

1. npm install nodemodule --save

then :

2. npm run seed

Solution 10:[10]

To resolve this error:

code: 'ERR_UNKNOWN_FILE_EXTENSION'

It's typically saying there is a need for an extension for ./bin/www file.

what you have to do is: add "type": "module", to your package.json and rename .bin/www to ./bin/www.js Restart your server

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