JavaScript String.prototype.toLocaleUpperCase() Method

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()
str.toLocaleUpperCase(locale) 

Parameters:

• locale: It is an optional parameter and this locale parameter indicates the locale to be used to convert to upper case according to any locale-specific case mappings.

Returns Value: This method returns a string of uppercase letters. 

Exceptions: This method gives two kinds of error, which are as follows:

• RangeError: If the locale argument isn’t a valid language tag.
• TypeError: If an array element isn’t of type string.

The below examples illustrate the String.prototype.toLocaleUpperCase() method in JavaScript: 

Example 1: In this example, we will convert some lowercase strings into uppercase letters using the String.prototype.toLocaleUpperCase() method in JavaScript.

javascript

<script>
    const gfg = 'GeeKsForGeekS';
    console.log('EN-US: ' + gfg.toLocaleUpperCase('en-US'));
    console.log('TR: ' + gfg.toLocaleUpperCase('tr'));

    const gfg1 = new String("String.prototype.toLocaleUpperCase()");
    console.log('Result: ' + gfg1.toLocaleUpperCase());
</script>

Output:

"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

<script>
    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');
</script>

Output:

"ALPHABET"
false
true
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 String.prototype.toLocaleUpperCase() method are listed below:

• Google Chrome
• Firefox
• IE
• Opera
• Safari
• Edge