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array.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

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
toLocaleString 1 12 1 5.5 4 1
Optional locales parameter 24 79 52 No 15 6.1
Optional options parameter 24 79 52 No 15 6.1
Mobile
Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
toLocaleString ≤37 18 4 10.1 1 1.0
Optional locales parameter ≤37 25 No 14 6.1 2.0
Optional options parameter ≤37 25 No 14 6.1 2.0
Server
Node.js
toLocaleString 0.1.100
Optional locales parameter 13.0.0
13.0.0
0.12
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 parameter 0.12

See also

© 2005–2018 Mozilla Developer Network and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://wiki.developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/toLocaleString