How can I determine a user's locale within the browser?

javascript

prompt-engineering

browser-locale

intl-api

byAlex Kataev·Sep 24, 2024

To quickly retrieve a user's locale, you can utilize the navigator.language for their primary language setting or the navigator.languages to retrieve all the preferred languages.

const userLocale = navigator.language;
console.log(userLocale); // Output: 'en-US'

const preferredLocales = navigator.languages;
console.log(preferredLocales); // Output: ['en-US', 'en', 'es']

Comprehensive locale detection

In some scenarios, the user's browser may not support the navigator.languages property. It's crucial to have a fallback strategy in such cases. The navigator.language or navigator.userLanguage provides the preferred language. When you hear "fallback", think "motivational poster" — never give up!

const userLocale = navigator.languages ? navigator.languages[0] : (navigator.language || navigator.userLanguage);
console.log(userLocale); // 'en-US' or browser's default language (hopefully they know the secret handshake)

Customizing with server-side headers

The HTTP Accept-Language header at the server side can provide localized content. However, what if the user wants to shake things up and change locales? Life's about choices, right?!

URL parameters: Incorporate language settings in the URL query, just like secret door in a spy movie.
Cookies: Store the user's language preferences as a treat for the user's next visit. Cookie or not-cookie? There is not question!
User selection: Include a feature for user's to change their language. It's like choosing between coffee and decaf.

Better formatting with Regional formats

Apart from language, the representation of dates, numbers, etc., vary across different locales. The Intl API can add a personal touch to these formats:

const numberFormat = new Intl.NumberFormat(userLocale);
console.log(numberFormat.format(123456.78)); // Output: '123,456.78' for 'en-US'

const dateFormat = new Intl.DateTimeFormat(userLocale);
console.log(dateFormat.format(new Date())); // Output: '12/31/2023' for 'en-US'

Checking browser and backward compatibility

Imagine going to a party, and they don't have your favorite snack! Bummer! That's why testing your codes in multiple browsers is important. Backward compatibility is also crucial, as not all users might have up-to-date browsers.

if ('Intl' in window) {
    const formatOptions = Intl.NumberFormat().resolvedOptions();  // Output: locale used by the Intl object
    console.log(formatOptions.locale); 
}