Getting error TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension "" for D:\Projects\matri-site\bin\www for Node Js v14

Question

I am new to Node js and got some issues. Previously I was using node Js v13.8 to run my express application and it was working very well. I was using es6 syntax and type module having JS extension files. But, when I upgraded to Node 14.1.0. It's showing the following error(Same error with 13.9 as well).

TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension "" for D:\Projects\matri-site\bin\www.

Here is my error snippet

Again when I downgraded to Node 13.8, it works fine.

Here is my package.json file :

{
  "name": "matri-site",
  "version": "0.0.0",
  "private": true,
  "type": "module",
  "scripts": {
    "start": "node ./bin/www"
  },
  "dependencies": {
    "bcryptjs": "^2.4.3",
    "buffer": "^5.5.0",
    "cookie-parser": "~1.4.4",
    "debug": "~2.6.9",
    "express": "4.16.1",
    "handlebars": "^4.7.6",
    "http-errors": "~1.6.3",
    "jade": "~1.11.0",
    "jsonwebtoken": "^8.5.1",
    "mongoose": "^5.8.9",
    "morgan": "~1.9.1",
    "nodemailer": "^6.4.2",
    "redis": "^3.0.2",
    "validator": "^12.1.0",
    "validatorjs": "^3.18.1"
  },
  "devDependencies": {
    "eslint": "^6.8.0"
  }
}

Here is my WWW file:

#!/usr/bin/env node

/**
 * Module dependencies.
 */

// var app = require('../app');
// var debug = require('debug')('matri-site:server');
// var http = require('http');

import app from '../app.js';
import debug from "debug";
 debug.debug('matri-site:server');
import http from "http";

/**
 * Get port from environment and store in Express.
 */

var port = normalizePort(process.env.PORT || '3000');
app.set('port', port);

/**
 * Create HTTP server.
 */

var server = http.createServer(app);

/**
 * Listen on provided port, on all network interfaces.
 */

server.listen(port);
server.on('error', onError);
server.on('listening', onListening);

/**
 * Normalize a port into a number, string, or false.
 */

function normalizePort(val) {
  var port = parseInt(val, 10);

  if (isNaN(port)) {
    // named pipe
    return val;
  }

  if (port >= 0) {
    // port number
    return port;
  }

  return false;
}

/**
 * Event listener for HTTP server "error" event.
 */

function onError(error) {
  if (error.syscall !== 'listen') {
    throw error;
  }

  var bind = typeof port === 'string'
    ? 'Pipe ' + port
    : 'Port ' + port;

  // handle specific listen errors with friendly messages
  switch (error.code) {
    case 'EACCES':
      console.error(bind + ' requires elevated privileges');
      process.exit(1);
      break;
    case 'EADDRINUSE':
      console.error(bind + ' is already in use');
      process.exit(1);
      break;
    default:
      throw error;
  }
}

/**
 * Event listener for HTTP server "listening" event.
 */

function onListening() {
  var addr = server.address();
  var bind = typeof addr === 'string'
    ? 'pipe ' + addr
    : 'port ' + addr.port;
  debug('Listening on ' + bind);
}

Answer 1

The real cause is due to the new specification on ESM support. That is, the file that contains #!/usr/bin/env node requires an extension when "type": "module". Native ESM requires .js extension to identify if it is ESM (you need to specify .cjs extension if your code is actually written in commonjs), which is why it was complaining about TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ""

That is, if you want to use native ESM, you will define "type": "module" in package.json and the file name must include .js extension, i.e. file.js. Otherwise, do not specify "type" (or specify "type": "commonjs") and the file name can be with or without the .js extension. For ESM under this case, you will need to have ".mjs" extension.