Web/JavaScript/Reference/Global objects/String/toUpperCase

The toUpperCase() method returns the calling string value converted to uppercase (the value will be converted to a string if it isn't one).

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Syntax

str.toUpperCase()

Return value

A new string representing the calling string converted to upper case.

Exceptions

TypeError

When called on null or undefined, for example, String.prototype.toUpperCase.call(undefined).

Description

The toUpperCase() method returns the value of the string converted to uppercase. This method does not affect the value of the string itself since JavaScript strings are immutable.

Examples

Basic usage

console.log('alphabet'.toUpperCase()); // 'ALPHABET'

Conversion of non-string this values to strings

This method will convert any non-string value to a string, when you set its this to a value that is not a string:

const a = String.prototype.toUpperCase.call({
  toString: function toString() {
    return 'abcdef';
  }
});

const b = String.prototype.toUpperCase.call(true);

// prints out 'ABCDEF TRUE'.
console.log(a, b);

Specifications

Specification

ECMAScript (ECMA-262)The definition of 'String.prototype.toUpperCase' in that specification.

Browser compatibility

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

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
toUpperCase	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support 3	Opera Full support 3	Safari Full support 1	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

Legend

Full support  

Full support

See also

• String.prototype.toLocaleLowerCase()
• String.prototype.toLocaleUpperCase()
• String.prototype.toLowerCase()

String.prototype.toUpperCase() by Mozilla Contributors is licensed under CC-BY-SA 2.5.