The toLocaleString() method returns a string with a language sensitive representation of this number.

The new locales and options arguments let applications specify the language whose formatting conventions should be used and customize the behavior of the function. In older implementations, which ignore the locales and options arguments, the locale used and the form of the string returned are entirely implementation dependent.


numObj.toLocaleString([locales [, options]])


Check the Browser compatibility section to see which browsers support the locales and options arguments, and the Example: Checking for support for locales and options arguments for feature detection.

Note: ECMAScript Internationalization API, implemented with Firefox 29, added the locales argument to the Number.toLocaleString() method. If the argument is undefined, this method returns localized digits specified by the OS, while the previous versions of Firefox returned Western Arabic digits. This change has been reported as a regression affecting backward compatibility which might be fixed soon. ()


Using toLocaleString

In basic use without specifying a locale, a formatted string in the default locale and with default options is returned.

var number = 3500;

console.log(number.toLocaleString()); // Displays "3,500" if in U.S. English locale

Checking for support for locales and options arguments

The locales and options arguments are not supported in all browsers yet. To check for support in ES5.1 and later implementations, the requirement that illegal language tags are rejected with a RangeError exception can be used:

function toLocaleStringSupportsLocales() {
  var number = 0;
  try {
  } catch (e) {
    return e​.name === 'RangeError';
  return false;

Prior to ES5.1, implementations were not required to throw a range error exception if toLocaleString is called with arguments.

A check that works in all hosts, including those supporting ECMA-262 prior to ed 5.1, is to test for the features specified in ECMA-402 that are required to support regional options for numObj.toLocaleString directly:

function toLocaleStringSupportsOptions() {
  return !!(typeof Intl == 'object' && Intl && typeof Intl.NumberFormat == 'function');

This tests for a global Intl object, checks that it's not null and that it has a NumberFormat property that is a function.

Using locales

This example shows some of the variations in localized number formats. In order to get the format of the language used in the user interface of your application, make sure to specify that language (and possibly some fallback languages) using the locales argument:

var number = 123456.789;

// German uses comma as decimal separator and period for thousands
// → 123.456,789

// Arabic in most Arabic speaking countries uses Eastern Arabic digits
// → ١٢٣٤٥٦٫٧٨٩

// India uses thousands/lakh/crore separators
// → 1,23,456.789

// the nu extension key requests a numbering system, e.g. Chinese decimal
// → 一二三,四五六.七八九

// when requesting a language that may not be supported, such as
// Balinese, include a fallback language, in this case Indonesian
console.log(number.toLocaleString(['ban', 'id']));
// → 123.456,789

Using options

The results provided by toLocaleString can be customized using the options argument:

var number = 123456.789;

// request a currency format
console.log(number.toLocaleString('de-DE', { style: 'currency', currency: 'EUR' }));
// → 123.456,79 €

// the Japanese yen doesn't use a minor unit
console.log(number.toLocaleString('ja-JP', { style: 'currency', currency: 'JPY' }))
// → ¥123,457

// limit to three significant digits
console.log(number.toLocaleString('en-IN', { maximumSignificantDigits: 3 }));
// → 1,23,000


When formatting large numbers of numbers, it is better to create a NumberFormat object and use the function provided by its NumberFormat.format property.

  Created by Mozilla Contributors, license: CC-BY-SA 2.5