Node.js script to count number of unique values in a very large CSV file

.js

const Papa = require("papaparse");
const fs = require("fs");

const FILE_NAME = "leads_modified_last7_days.csv";
const COLUMN_NAME = "LastModifiedById";

const file = fs.createReadStream(FILE_NAME);
const createdByIdCount = {};
let count = 0;

Papa.parse(file, {
  header: true,
  step: function (row) {
    count++;

    if (!createdByIdCount[row.data[COLUMN_NAME]]) {
      createdByIdCount[row.data[COLUMN_NAME]] = 0;
    }

    createdByIdCount[row.data[COLUMN_NAME]] += 1;

    // little progress output
    if (count % 250000 == 0) {
      console.log(count + " rows processed");
    }
  },
  complete: function () {
    console.log(createdByIdCount);
  },
});

// package.json 
// {
//   "dependencies": {
//     "papaparse": "5.3.2"
//   }
// }