let exp_number = 449272783789821;
let exp_string = exp_number.toLocaleString("en-US");
console.log(exp_string);

let float_number = 3419244.546;
let exp_string1 = float_number.toLocaleString("en-US");
console.log(exp_string1);

function float_number(number1) {
  return number1.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ',');
}

let exp_number = float_number(6723141.141);
console.log(exp_number);

let example_number = 2224446668886;

// England uses commas as decimal separators and periods for thousands
let fixed_Number = new Intl.NumberFormat('en-EN');
console.log(fixed_Number.format(example_number));

// Italy uses dots as decimal separators and periods for thousands
fixed_Number = new Intl.NumberFormat('it-IT');
console.log(fixed_Number.format(example_number));

// Arabic in most Arabic-speaking countries uses absolute Arabic digits
fixed_Number = new Intl.NumberFormat('ar-EG');
console.log(fixed_Number.format(example_number));

// India uses thousands/lakh/crore separators
fixed_Number = new Intl.NumberFormat('en-IN');
console.log(fixed_Number.format(example_number));

// I: ADD A COMMA TO SEPARATE THE GIVEN NUMBER
// number: original number
// per: add comma per n digits (default 3)
// places: number of decimal places (default 3)
function insert_comma (number, per, places) {

  // 1 - Set defaults
  if (per==undefined) { per = 3; }
  if (places==undefined) { places = 3; }

  // 2 - No decimal places - round off
  // Remove this if you don't want to round off
  if (places==0) { number = Math.round(number); }

  // 3- Split whole and decimal numbers
    var ex_str = number.toString(),
      ex_Dot = ex_str.indexOf("."),
      ex_Whole = "", ex_Decimal = "";

  if (ex_Dot == -1) {
    ex_Whole = ex_str;
    ex_Decimal = 0;

  } else {
    ex_Whole = ex_str.substring(0, ex_Dot);
    ex_Decimal = ex_str.substring(ex_Dot+1);
  }

  // 4 - Add commas to the whole number
    var add_Comma = "", count = 0;

  if (ex_Whole.length > per) { for (let i=(ex_Whole.length-1); i>=0; i--) {
    add_Comma = ex_Whole.charAt(i) + add_Comma;
    count++;

    if (count == per && i!=0) {
      add_Comma = "," + add_Comma;
      count = 0;
    }

  }} else { add_Comma = ex_Whole; }

  // 5 - Round off to given decimal places
  if (places==0) { ex_Decimal = ""; }

  else {
    ex_Decimal = +("0." + ex_Decimal);
    ex_Decimal = ex_Decimal.toFixed(places).toString().substring(1);
  }

  // 6 - Return "whole with a comma" plus decimal places
  return add_Comma + ex_Decimal;
}

// II: TEST
// 1 - Whole number
var whole_num = 3336669997;
console.log(insert_comma(whole_num));
console.log(insert_comma(whole_num, 3, 0));

// 2 - Decimal
var dec_num = 24680.213;
console.log(insert_comma(dec_num));
console.log(insert_comma(dec_num, 3, 0));