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

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 Status Comment
ECMAScript 1st Edition (ECMA-262) Standard Initial definition. Implemented in JavaScript 1.0.
ECMAScript 5.1 (ECMA-262)
The definition of 'String.prototype.toUpperCase' in that specification.
Standard  
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'String.prototype.toUpperCase' in that specification.
Standard  
ECMAScript Latest Draft (ECMA-262)
The definition of 'String.prototype.toUpperCase' in that specification.
Draft  

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
toUpperCaseChrome Full support YesEdge Full support 12Firefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes

Legend

Full support  
Full support

See also

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