Number.prototype.toLocaleString()

function eArabic(x) {
  return x.toLocaleString("ar-EG");
}

console.log(eArabic(123456.789));
// Expected output: ""

console.log(eArabic("123456.789"));
// Expected output: "123456.789"

console.log(eArabic(NaN));
// Expected output: " "

toLocaleString()
toLocaleString(locales)
toLocaleString(locales, options)

var number = 3500;

console.log(number.toLocaleString()); //  '3,500'   U.S. English

function toLocaleStringSupportsLocales() {
  return (
    typeof Intl === "object" &&
    !!Intl &&
    typeof Intl.DateTimeFormat === "function"
  );
}

var number = 123456.789;

//           ,      
console.log(number.toLocaleString("de-DE"));
// 123.456,789

//           ,      
console.log(number.toLocaleString("ru-RU"));
// 123 456,789

//        
console.log(number.toLocaleString("ar-EG"));
// 

//      //
console.log(number.toLocaleString("en-IN"));
// 1,23,456.789

//   nu   , ,  
console.log(number.toLocaleString("zh-Hans-CN-u-nu-hanidec"));
// ,.

//      , 
// ,    ,    
console.log(number.toLocaleString(["ban", "id"]));
// 123.456,789

var number = 123456.789;

//   
console.log(
  number.toLocaleString("de-DE", { style: "currency", currency: "EUR" }),
);
// 123.456,79 

console.log(
  number.toLocaleString("ru-RU", { style: "currency", currency: "RUB" }),
);
// 123 456,79 

//      
console.log(
  number.toLocaleString("ja-JP", { style: "currency", currency: "JPY" }),
);
// 123,457

//     
console.log(number.toLocaleString("en-IN", { maximumSignificantDigits: 3 }));
// 1,23,000

//        
const num = 30000.65;
console.log(
  num.toLocaleString(undefined, {
    minimumFractionDigits: 2,
    maximumFractionDigits: 2,
  }),
);
// "30,000.65"      
// "30.000,65"      
// "30 000,65"