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

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

Specification Status Comment
ECMAScript 3rd Edition (ECMA-262) Standard Initial definition. Implemented in JavaScript 1.2.
ECMAScript 5.1 (ECMA-262)
The definition of 'String.prototype.toLocaleUpperCase' in that specification.
Standard  
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'String.prototype.toLocaleUpperCase' in that specification.
Standard  
ECMAScript Latest Draft (ECMA-262)
The definition of 'String.prototype.toLocaleUpperCase' in that specification.
Draft  
ECMAScript Internationalization API 4.0 (ECMA-402)
The definition of 'String.prototype.toLocaleUpperCase' in that specification.
Draft ES Intl 2017 added the locale parameter.

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
Basic supportChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
localeChrome ? Edge ? Firefox Full support 55IE ? Opera ? Safari ? WebView Android ? Chrome Android ? Edge Mobile ? Firefox Android Full support 55Opera Android ? Safari iOS ? Samsung Internet Android ? nodejs ?

Legend

Full support  
Full support
Compatibility unknown  
Compatibility unknown

See also

Document Tags and Contributors

Last updated by: wbamberg,