count-files.mjs

import {readdir, stat} from 'fs/promises';
import path from 'path';

const dir = process.argv[2];

async function listFiles(dir) {
  const subdirs = await readdir(dir);
  const files = await Promise.all(subdirs.map(async (subdir) => {
    const res = path.resolve(dir, subdir);
    return (await stat(res)).isDirectory() ? listFiles(res) : res;
  }));
  return files.reduce((a, f) => a.concat(f), []);
}

const countByExt = new Map();

for (const file of await listFiles(dir)) {
	const ext = path.extname(file);

	countByExt.set(ext, (countByExt.get(ext) ?? 0) + 1);
}

console.log('Count per file extension:');
const entries = Array.from(countByExt.entries())
	.sort((a, b) => b[1] - a[1]);

for (const [ext, count] of entries) {
	console.log((ext || 'no extension') + ': ' + count)
}