find-duplicate-case-sensitive-files.js

'use strict';
let fs = require('fs');
let directory = process.argv[2];
let map = {};
let duplicates = {};

fs.readdir(directory, (err, items) => {
  for (let i = 0; i < items.length; i++) {
    let key = items[i].toLowerCase();

    if (map.hasOwnProperty(key)) {
      map[key].push(items[i]);
    }
    else {
      map[key] = [items[i]];
    }
  }

  Object.keys(map).forEach((key) => {
    if (map[key].length > 1) {
      duplicates[key] = map[key];
    }
  });

  console.log(duplicates);
});