JavaScript Object.toLocaleString()

const number = 123456.789;

// convert number to string with a language-sensitive
// representation for the Indian English locale
const numberString = number.toLocaleString('en-IN');

console.log(numberString);
// Output: 1,23,456.789

toLocaleString() Syntax

The syntax of the toLocaleString() method is:

obj.toLocaleString(Locales, options)

Here, obj is the object whose language-specific string representation is required.

toLocaleString() Parameters

The toLocaleString() method does not take in any parameters by default. However, it can have optional parameters:

• Locales - specifies which language format to use, such as en-US (American English), en-IN (Indian English) and so on
• options - object that helps set some properties to customize the string representation

Note: The Locales and options arguments customize the behavior of the function to specify the desired formatting conventions based on the language or region.

toLocaleString() Return Value

The toLocaleString() method returns a string representing the object.

Some objects overriding Object.toLocaleString():

• Array: JavaScript Array.toLocaleString()
• Number: JavaScript Number.toLocaleString()

Example 1: JavaScript toLocaleString() With Array

// create an array of three numbers
const arr = [4, 7, 10];

// converts to string in French currency format (Euros)
let string = arr.toLocaleString("fr", { style: "currency", currency: "EUR" });

console.log(string);

// Output: 4,00 €,7,00 €,10,00 €

In the above example, the toLocaleString() converts the array arr into a formatted string having currency format for the French Locale and using Euros as the currency symbol.

In the above code, fr represents the French locale and EUR represents the Euro currency.

Example 2: toLocaleString() Method With Number

// create a number
const num = 123456.789;

// convert num to string in
// Indian English formatting convention
console.log(num.toLocaleString("en-IN"));

 // India uses thousand / lakh / crore separators
// Output: 1,23,456.789

Example 3: toLocaleString() Method With Date

// create a new date object
const date = new Date(Date.now());
console.log(date); 

// Output: Fri Mar 03 2022 12:30:00 GMT-0800 (Pacific Standard Time)

// convert the date using German locale formatting convention 
let dateStr = date.toLocaleString("de");
console.log(dateStr);
 

// Output: 29.7.2020, 15:37:00

Note: The Object.toLocaleString() method usually returns the result of toString(). This method is meant to be overridden by derived objects for locale-specific purposes, even though all may not use it.

Recommended Reading:

• JavaScript.Object.toString()