String.prototype.toUpperCase() - JavaScript | MDN (original) (raw)

Baseline

Widely available

The toUpperCase() method of String values returns this string converted to uppercase.

Try it

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

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 itsthis 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

Browser compatibility

See also