Object.prototype.toLocaleString()

The toLocaleString() method of Object instances returns a string representing this object. This method is meant to be overridden by derived objects for locale-specific purposes.

Syntax

toLocaleString()

Parameters

None. However, all objects that override this method are expected to accept at most two parameters, corresponding to locales and options, such as Date.prototype.toLocaleString. The parameter positions should not be used for any other purpose.

Return value

The return value of calling this.toString().

Description

All objects that inherit from Object.prototype (that is, all except null-prototype objects) inherit the toLocaleString() method. Object's toLocaleString returns the result of calling this.toString().

This function is provided to give objects a generic toLocaleString method, even though not all may use it. In the core language, these built-in objects override toLocaleString to provide locale-specific formatting:

Examples

Using the base toLocaleString() method

The base toLocaleString() method simply calls toString().

const obj = {
  toString() {
    return "My Object";
  },
};
console.log(obj.toLocaleString()); // "My Object"

Array toLocaleString() override

Array.prototype.toLocaleString is used to print array values as a string by invoking each element's toLocaleString() method and joining the results with a locale-specific separator. For example:

const testArray = [4, 7, 10];

const euroPrices = testArray.toLocaleString("fr", {
  style: "currency",
  currency: "EUR",
});
// "4,00 €,7,00 €,10,00 €"

Date toLocaleString() override

Date.prototype.toLocaleString is used to print out date displays more suitable for specific locales. For example:

const testDate = new Date();
// "Fri May 29 2020 18:04:24 GMT+0100 (British Summer Time)"

const deDate = testDate.toLocaleString("de");
// "29.5.2020, 18:04:24"

const frDate = testDate.toLocaleString("fr");
// "29/05/2020, 18:04:24"

Number toLocaleString() override

Number.prototype.toLocaleString is used to print out number displays more suitable for specific locales, e.g. with the correct separators. For example:

const testNumber = 2901234564;
// "2901234564"

const deNumber = testNumber.toLocaleString("de");
// "2.901.234.564"

const frNumber = testNumber.toLocaleString("fr");
// "2 901 234 564"