String.prototype.toUpperCase()

The toUpperCase() method of {{jsxref("String")}} values returns this string converted to uppercase.

{{InteractiveExample("JavaScript Demo: String.prototype.toUpperCase()", "shorter")}}

```js interactive-example const sentence = "The quick brown fox jumps over the lazy dog.";

console.log(sentence.toUpperCase()); // Expected output: "THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG."

## Syntax

```js-nolint
toUpperCase()

Parameters#

None.

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#

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() {
    return "abcdef";
  },
});

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

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

Specifications#

{{Specifications}}

Browser compatibility#

{{Compat}}

See also#

• {{jsxref("String.prototype.toLocaleLowerCase()")}}
• {{jsxref("String.prototype.toLocaleUpperCase()")}}
• {{jsxref("String.prototype.toLowerCase()")}}