String.prototype.toLocaleUpperCase()

The toLocaleUpperCase() method returns the calling string value converted to upper case, according to any locale-specific case mappings.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

Syntax

str.toLocaleUpperCase()
str.toLocaleUpperCase(locale)
str.toLocaleUpperCase([locale, locale, ...])

Parameters

locale Optional

The locale parameter indicates the locale to be used to convert to upper case according to any locale-specific case mappings. If multiple locales are given in an Array, the best available locale is used. The default locale is the host environment’s current locale.

Return value

A new string representing the calling string converted to upper case, according to any locale-specific case mappings.

Exceptions

• A RangeError ("invalid language tag: xx_yy") is thrown if a locale argument isn't a valid language tag.
• A TypeError ("invalid element in locales argument") is thrown if an array element isn't of type string.

Description

The toLocaleUpperCase() method returns the value of the string converted to upper case according to any locale-specific case mappings. toLocaleUpperCase() does not affect the value of the string itself. In most cases, this will produce the same result as toUpperCase(), but for some locales, such as Turkish, whose case mappings do not follow the default case mappings in Unicode, there may be a different result.

Also notice that conversion is not necessarily a 1:1 character mapping, as some characters might result in two (or even more) characters when transformed to upper-case. Therefore the length of the result string can differ from the input length. This also implies that the conversion is not stable, so i.E. the following can return false:
x.toLocaleLowerCase() === x.toLocaleUpperCase().toLocaleLowerCase()

Examples

Using toLocaleUpperCase()

'alphabet'.toLocaleUpperCase(); // 'ALPHABET'

'Gesäß'.toLocaleUpperCase(); // 'GESÄSS'

'i\u0307'.toLocaleUpperCase('lt-LT'); // 'I'

let locales = ['lt', 'LT', 'lt-LT', 'lt-u-co-phonebk', 'lt-x-lietuva'];
'i\u0307'.toLocaleUpperCase(locales); // 'I'

Specifications

Browser compatibility

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

See also

• String.prototype.toLocaleLowerCase()
• String.prototype.toLowerCase()
• String.prototype.toUpperCase()