Last Updated : 12 Jul, 2025
The String.prototype.toLocaleLowerCase() method in JavaScript is a Standard built-in object which returns the calling string value converted to a lowercase letter on the basis of the host's current locale.
Syntax:str.toLocaleLowerCase()Parameters:
str.toLocaleLowerCase(locale)
This method returns a string of lowercase letters.
Exceptions:This method gives two kinds of errors, which are as follows:
The below examples illustrate the String.prototype.toLocaleLowerCase() method in JavaScript:
Example 1: In this example, we will convert the uppercase string to a lowercase string and console it using the String.prototype.toLocaleLowerCase() method in JavaScript.
javascript
// Input string
let gfg = 'GeeKsForGeekS';
// Output with lowercase method
console.log('EN-US: ' + gfg.toLocaleLowerCase('en-US'));
console.log('TR: ' + gfg.toLocaleLowerCase('tr'));
// New input string
let gfg1 = new String("String.prototype.toLocaleLowerCase()");
// Display output
console.log('Result: ' + gfg1.toLocaleLowerCase());
EN-US: geeksforgeeks TR: geeksforgeeks Result: string.prototype.tolocalelowercase()
Example 2: In this example, we will convert the uppercase string to a lowercase string and console it using the String.prototype.toLocaleLowerCase() method in JavaScript.
javascript
console.log('ALPHABET'.toLocaleLowerCase());
console.log('\u0130'.toLocaleLowerCase('tr') === 'i');
console.log('\u0130'.toLocaleLowerCase('en-US') === 'i');
let geeks = ['tr', 'TR', 'tr-TR', 'tr-u-co-search', 'tr-x-turkish'];
console.log('\u0130'.toLocaleLowerCase(geeks) === 'i');
alphabet true false true
We have a complete list of Javascript String methods, to check those please go through this JavaScript String Complete Reference article.
Supported Browsers:The browsers supported by the String.prototype.toLocaleLowerCase() method are listed below:
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HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4