String.prototype.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).

Try it

Syntax

js

toUpperCase()

Return value

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

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

js

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:

js

const a = String.prototype.toUpperCase.call({
  toString() {
    return "abcdef";
  },
});

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

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

Specifications

Specification
ECMAScript Language Specification
# sec-string.prototype.touppercase

Browser compatibility

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See also