How to use ES6 import on nodejs proejct (Node.js/IISNode)

First, create a run.cjs file and update this file to import your nodejs site entry point file (server.js) and configure it as the iisnode's entry point ( in web.config).

run.cjs:

import("./server.js");

The cjs file extension is important because it tells Node that this file is not an ES module, as it would expect because of "type": "module" in the package.json. It allows other CommonJS files to include our new file - namely iisnode's interceptor.js. It again imports the server.js which then runs fine as ES module.

Below is a demo entry point file server.js.

server.js:

import express from 'express';
  
const app = express();
  
app.get('/',(req,res) => {
const body = "hello this is a ES6 import demo project"
// Adds header
res.append('Content-Type', 'text/plain;charset=utf-8');
res.append('Connection', 'keep-alive')
res.append('Set-Cookie', 'divehours=fornightly')
res.append('Content-Length', Buffer.byteLength(body, 'utf-8'));
res.status(200).send(body);
})
  
const PORT = process.env.PORT;
  
app.listen(PORT,() => {
    console.log(`Running on PORT ${PORT}`);
})

The below code will set your site default routing for iisnode.

web.config:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <system.webServer>
        <handlers>
            <add name="iisnode" path="run.cjs" verb="*" modules="iisnode" />
        </handlers>
		<rewrite>
      <rules>
        <!-- All other URLs are mapped to the node.js site entry point -->
        <rule name="DynamicContent">
          <conditions>
            <add input="{REQUEST_FILENAME}" matchType="IsFile" negate="True"/>
          </conditions>
          <action type="Rewrite" url="run.cjs"/>
        </rule>
      </rules>
    </rewrite>
    </system.webServer>
</configuration>

package.json:

{
    "name": "index",
    "version": "1.0.0",
    "description": "",
    "main": "server.js",
    "type": "module",
    "scripts": {
      "test": "echo \"Error: no test specified\" && exit 1",
      "start": "node --experimental-modules server.js"
    },
    "keywords": [],
    "author": "",
    "license": "ISC",
    "dependencies": {
        "express": "^4.18.1"
    }
  }

 Now your site will auto redirect to run.cjs file and auto enter your site entry point file (server.js).