How to get root directory path using Express JS Code

How to print or get the root project folder path while coding in express JS. The root folder is the main project folder where the domainame.com/ points to.

__dirname is express used to get the root directory.

Eg: console.log(__dirname);

const express = require("express");
const app = express();

app.get("/", function(req, res){
   console.log(__dirname);
               //gets the root directory
});
app.listen(4000, function(){
    console.log("Server started at port 4000");
});