javascript instance method

String.prototype.toUpperCase()

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

Interactive exampleOpen the canonical MDN source to run this embedded demo.

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

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

SpecificationsStandards references are available on the canonical MDN page.

Browser compatibility

Browser compatibilityCompatibility data is available on the canonical MDN page.