Web/JavaScript/Reference/Global objects/String/toLocaleLowerCase

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

Syntax

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

Parameters

locale Optional: The locale parameter indicates the locale to be used to convert to lower 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 lower 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 toLocaleLowerCase() method returns the value of the string converted to lower case according to any locale-specific case mappings. toLocaleLowerCase() does not affect the value of the string itself. In most cases, this will produce the same result as toLowerCase(), 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.

Examples

Using toLocaleLowerCase()

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

'\u0130'.toLocaleLowerCase('tr') === 'i';    // true
'\u0130'.toLocaleLowerCase('en-US') === 'i'; // false

let locales = ['tr', 'TR', 'tr-TR', 'tr-u-co-search', 'tr-x-turkish'];
'\u0130'.toLocaleLowerCase(locales) === 'i'; // true

Specifications

Specification
ECMAScript (ECMA-262)The definition of 'String.prototype.toLocaleLowerCase' in that specification.
ECMAScript Internationalization API (ECMA-402)The definition of 'String.prototype.toLocaleLowerCase' in that specification.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
`toLocaleLowerCase`	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support 5.5	Opera Full support 4	Safari Full support 1.3	WebView Android Full support 1	Chrome Android Full support 18	Firefox Android Full support 4	Opera Android Full support 10.1	Safari iOS Full support 1	Samsung Internet Android Full support 1.0	nodejs Full support 0.1.100
`locale`	Chrome Full support 58	Edge Full support 12	Firefox Full support 55	IE Full support 6	Opera Full support 45	Safari Full support 10	WebView Android Full support 58	Chrome Android Full support 58	Firefox Android Full support 55	Opera Android Full support 43	Safari iOS Full support 10	Samsung Internet Android Full support 7.0	nodejs Full support 13.0.0 Full support 13.0.0 Partial support 0.12 Notes' Notes' Before version 13.0.0, only the locale data for `en-US` is available by default. When other locales are specified, the function silently falls back to `en-US`. To make full ICU (locale) data available for versions prior to 13, see Node.js documentation on the `--with-intl` option and how to provide the data.

Legend

Full support: Full support
See implementation notes.': See implementation notes.