JavaScript toLocaleString method

last modified April 4, 2025

In this article we show how to format numbers and dates using the toLocaleString method in JavaScript.

Localization in JavaScript

The toLocaleString method converts a number or date into a string, using locale-specific conventions. It provides a way to format data according to the user’s language and region settings.

This method is available on Number, Date, and Array objects in JavaScript. The formatting rules vary based on the host’s current locale or the locale specified in the options parameter.

For numbers, it handles decimal separators, grouping of digits, and currency formatting. For dates, it formats according to local conventions for date and time representation. The method is essential for internationalized applications.

Basic number formatting

The following example demonstrates basic number formatting with toLocaleString.

main.js

const number = 123456.789;

console.log(number.toLocaleString()); // Default locale console.log(number.toLocaleString(‘de-DE’)); // German format console.log(number.toLocaleString(‘ar-EG’)); // Arabic format

We format the same number using different locales. The method automatically adjusts decimal points, grouping separators, and digit representation based on locale conventions.

$ node main.js “123,456.789” (en-US) “123.456,789” (de-DE) “١٢٣٬٤٥٦٫٧٨٩” (ar-EG)

Currency formatting

The toLocaleString method can format numbers as currency values.

main.js

const price = 1234.56;

console.log(price.toLocaleString(’en-US’, { style: ‘currency’, currency: ‘USD’ }));

console.log(price.toLocaleString(‘ja-JP’, { style: ‘currency’, currency: ‘JPY’ }));

We format numbers as currency values for different locales. The style option specifies currency formatting, while the currency option defines which currency to use.

$ node main.js “$1,234.56” (en-US) “￥1,235” (ja-JP)

Date formatting

The toLocaleString method can format Date objects according to locale conventions.

main.js

const date = new Date();

console.log(date.toLocaleString()); // Default locale console.log(date.toLocaleString(’en-GB’)); // British format console.log(date.toLocaleString(‘ko-KR’)); // Korean format

We format the current date and time using different locales. The method adjusts the date order, separators, and time format based on regional conventions.

$ node main.js “4/4/2025, 3:14:07 PM” (en-US) “04/04/2025, 15:14:07” (en-GB) “2025. 4. 4. 오후 3:14:07” (ko-KR)

Custom date formatting

We can customize date formatting using options with toLocaleString.

main.js

const date = new Date();

const options = { weekday: ’long’, year: ’numeric’, month: ’long’, day: ’numeric’ };

console.log(date.toLocaleString(‘de-DE’, options)); console.log(date.toLocaleString(‘fr-FR’, options));

We specify formatting options to control how the date is displayed. The options object lets us choose which components to include and their format style.

$ node main.js “Freitag, 4. April 2025” (de-DE) “vendredi 4 avril 2025” (fr-FR)

Array localization

The toLocaleString method can also be called on arrays to format all elements.

main.js

const mixedArray = [12345.67, new Date(), ‘plain string’];

console.log(mixedArray.toLocaleString(’en-US’)); console.log(mixedArray.toLocaleString(’es-ES’));

When called on an array, toLocaleString calls the method on each element. Numbers and dates are formatted according to locale, while strings remain unchanged.

$ node main.js “12,345.67,4/4/2025, 3:14:07 PM,plain string” (en-US) “12.345,67,4/4/2025 15:14:07,plain string” (es-ES)

Source

Number toLocaleString - language reference

In this article we have demonstrated how to use the toLocaleString() method to format numbers and dates in JavaScript according to locale conventions.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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