Last Updated : 12 Jul, 2025
The String.prototype.toLocaleUpperCase() method in JavaScript is a Standard built-in object which returns the calling string value converted to the uppercase letter on the basis of the host's current locale. This method mostly returns a similar result as the string toUppercase() method
Syntax:str.toLocaleUpperCase()Parameters:
str.toLocaleUpperCase(locale)
This method returns a string of uppercase letters.
Exceptions:This method gives two kinds of errors, which are as follows:
Example 1: In this example, we will convert some lowercase strings into uppercase letters using the String.prototype.toLocaleUpperCase() method in JavaScript.
javascript
// Input string
let gfg = 'GeeKsForGeekS';
// Display output with upper case
console.log('EN-US: ' + gfg.toLocaleUpperCase('en-US'));
console.log('TR: ' + gfg.toLocaleUpperCase('tr'));
// New input string
let gfg1 = new String("String.prototype.toLocaleUpperCase()");
// Display output with upper case
console.log('Result: ' + gfg1.toLocaleUpperCase());
EN-US: GEEKSFORGEEKS TR: GEEKSFORGEEKS Result: STRING.PROTOTYPE.TOLOCALEUPPERCASE()
Example 2: In this example, we will convert some lowercase strings into uppercase letters using the String.prototype.toLocaleUpperCase() method in JavaScript.
javascript
console.log('ALPHABET'.toLocaleUpperCase());
console.log('i\u0307'.toLocaleUpperCase('tr') === 'I');
console.log('i\u0307'.toLocaleUpperCase('lt-LT') === 'I');
let geeks = ['lt', 'LT', 'lt-LT', 'lt-u-co-phonebk', 'lt-x-lietuva'];
console.log('i\u0307'.toLocaleUpperCase(geeks) === 'I');
ALPHABET false true trueSupported Browsers:
The browsers supported by the String.prototype.toLocaleUpperCase() method are listed below:
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HTML:
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