Array.prototype.toLocaleString()

The toLocaleString() method returns a string representing the elements of the array. The elements are converted to Strings using their toLocaleString methods and these Strings are separated by a locale-specific String (such as a comma “,”).

Syntax

arr.toLocaleString([locales[, options]]);

Parameters

locales Optional
A string with a BCP 47 language tag, or an array of such strings. For the general form and interpretation of the locales argument, see the Intl page.
options Optional
An object with configuration properties, for numbers see Number.prototype.toLocaleString(), and for dates see Date.prototype.toLocaleString().

Return value

A string representing the elements of the array.

Polyfill

// https://tc39.github.io/ecma402/#sup-array.prototype.tolocalestring
if (!Array.prototype.toLocaleString) {
  Object.defineProperty(Array.prototype, 'toLocaleString', {
    value: function(locales, options) {
      // 1. Let O be ? ToObject(this value).
      if (this == null) {
        throw new TypeError('"this" is null or not defined');
      }

      var a = Object(this);

      // 2. Let len be ? ToLength(? Get(A, "length")).
      var len = a.length >>> 0;

      // 3. Let separator be the String value for the
      //    list-separator String appropriate for the
      //    host environment's current locale (this is
      //    derived in an implementation-defined way).
      // NOTE: In this case, we will use a comma
      var separator = ',';

      // 4. If len is zero, return the empty String.
      if (len === 0) {
        return '';
      }

      // 5. Let firstElement be ? Get(A, "0").
      var firstElement = a[0];
      // 6. If firstElement is undefined or null, then
      //  a.Let R be the empty String.
      // 7. Else,
      //  a. Let R be ?
      //     ToString(?
      //       Invoke(
      //        firstElement,
      //        "toLocaleString",
      //        « locales, options »
      //       )
      //     )
      var r = firstElement == null ?
        '' : firstElement.toLocaleString(locales, options);

      // 8. Let k be 1.
      var k = 1;

      // 9. Repeat, while k < len
      while (k < len) {
        // a. Let S be a String value produced by
        //   concatenating R and separator.
        var s = r + separator;

        // b. Let nextElement be ? Get(A, ToString(k)).
        var nextElement = a[k];

        // c. If nextElement is undefined or null, then
        //   i. Let R be the empty String.
        // d. Else,
        //   i. Let R be ?
        //     ToString(?
        //       Invoke(
        //        nextElement,
        //        "toLocaleString",
        //        « locales, options »
        //       )
        //     )
        r = nextElement == null ?
          '' : nextElement.toLocaleString(locales, options);

        // e. Let R be a String value produced by
        //   concatenating S and R.
        r = s + r;

        // f. Increase k by 1.
        k++;
      }

      // 10. Return R.
      return r;
    }
  });
}

If you need to support truly obsolete JavaScript engines that don't support Object.defineProperty, it's best not to polyfill Array.prototype methods at all, as you can't make them non-enumerable.

Examples

Using locales and options

The elements of the array are converted to strings using their toLocaleString methods.

Always display the currency for the strings and numbers in the prices array:

var prices = ['¥7', 500, 8123, 12];
prices.toLocaleString('ja-JP', { style: 'currency', currency: 'JPY' });

// "¥7,¥500,¥8,123,¥12"

For more examples, see also the Intl, NumberFormat, and DateTimeFormat pages.

Specifications

Specification
ECMAScript (ECMA-262)
The definition of 'Array.prototype.toLocaleString' in that specification.
ECMAScript Internationalization API (ECMA-402)
The definition of 'Array.prototype.toLocaleString' in that specification.

Browser compatibility

DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
toLocaleStringChrome Full support 1Edge Full support 12Firefox Full support 1IE Full support 5.5Opera Full support 4Safari Full support 1WebView Android Full support ≤37Chrome Android Full support 18Firefox Android Full support 4Opera Android Full support 10.1Safari iOS Full support 1Samsung Internet Android Full support 1.0nodejs Full support 0.1.100
Optional locales parameterChrome Full support 24Edge Full support 79Firefox Full support 52IE No support NoOpera Full support 15Safari Full support 6.1WebView Android Full support ≤37Chrome Android Full support 25Firefox Android No support NoOpera Android Full support 14Safari iOS Full support 6.1Samsung Internet Android Full support 2.0nodejs Full support 13.0.0
Full support 13.0.0
Partial support 0.12
Notes
Notes Before version 13.0.0, only the locale data for en-US is available by default. When other locales are specified, the function silently falls back to en-US. To make full ICU (locale) data available for versions prior to 13, see Node.js documentation on the --with-intl option and how to provide the data.
Optional options parameterChrome Full support 24Edge Full support 79Firefox Full support 52IE No support NoOpera Full support 15Safari Full support 6.1WebView Android Full support ≤37Chrome Android Full support 25Firefox Android No support NoOpera Android Full support 14Safari iOS Full support 6.1Samsung Internet Android Full support 2.0nodejs Full support 0.12

Legend

Full support
Full support
No support
No support
See implementation notes.
See implementation notes.

See also