user: write me a program in nodejs with express and ejs. i want it to recursively scan a directory, and serve a nested list of files and folders as a webpage

assistant: Sure! Here is an example program in Node.js using Express and EJS that recursively scans a directory and serves a nested list of files and folders as a webpage:

```
const express = require('express');
const app = express();
const ejs = require('ejs');
const path = require('path');
const fs = require('fs');

// Set the views directory and the view engine
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'ejs');

// Define the route for the directory listing
app.get('/list/:dir(*)', (req, res) => {
  // Get the directory path from the URL parameter
  const dirPath = path.join(__dirname, req.params.dir);

  // Check if the directory exists
  if (fs.existsSync(dirPath)) {
    // Read the contents of the directory
    const files = fs.readdirSync(dirPath);

    // Create an array to hold the nested list data
    const listData = [];

    // Iterate over each file/folder in the directory
    files.forEach(file => {
      // Construct the full path to the file/folder
      const filePath = path.join(dirPath, file);

      // Check if the item is a directory
      if (fs.statSync(filePath).isDirectory()) {
        // Recursively call this function to get the nested list of the subdirectory
        const nestedList = getNestedList(filePath);

        // Add the nested list data to the current item
        listData.push({ name: file, type: 'directory', items: nestedList });
      } else {
        // Add the file data to the current item
        listData.push({ name: file, type: 'file' });
      }
    });

    // Render the EJS template with the nested list data
    res.render('list', { dirPath, listData });
  } else {
    // If the directory does not exist, return a 404 error
    res.status(404).send('Directory not found');
  }
});

// Define the function to recursively get the nested list of a directory
function getNestedList(dirPath) {
  // Read the contents of the directory
  const files = fs.readdirSync(dirPath);

  // Create an array to hold the nested list data
  const nestedList = [];

  // Iterate over each file/folder in the directory
  files.forEach(file => {
    // Construct the full path to the file/folder
    const filePath = path.join(dirPath, file);

    // Check if the item is a directory
    if (fs.statSync(filePath).isDirectory()) {
      // Recursively call this function to get the nested list of the subdirectory
      const subList = getNestedList(filePath);

      // Add the nested list data to the current item
      nestedList.push({ name: file, type: 'directory', items: subList });
    } else {
      // Add the file data to the current item
      nestedList.push({ name: file, type: 'file' });
    }
  });

  // Return the nested list data
  return nestedList;
}

// Start the server on port 3000
app.listen(3000, () => console.log('Server started on port 3000'));
```

This program defines a route `/list/:dir(*)` that takes a directory path as a parameter and returns a webpage with a nested list of files and folders in that directory. The `getNestedList()` function is used to recursively scan the directory and construct the nested list data. The EJS template `views/list.ejs` is used to render the webpage with the nested list data.

Note: This program assumes that the directory being scanned is a local directory on the server running the Node.js application. If you want to scan a directory on a remote server or from a client-side web application, you will need to modify the program accordingly.