Find duplicates in a file

find_duplicates.js

const fs = require("fs");

const filePath = process.argv[2];

if (!filePath) {
  console.error("Please provide a file path");
  process.exit(1);
}

const data = fs.readFileSync(filePath, "utf8");
const data_array = data.trim().split("\n");

const duplicates = data_array.filter((item, index, self) => {
  return self.indexOf(item) !== index;
});

console.log(duplicates);