String

`String.prototype.toUpperCase`

Returns the calling string value converted to uppercase

Syntax

JavaScript

string.toUpperCase()

Return Value

A new string with all characters converted to uppercase

Examples

Basic Usage

const str = 'hello world';
console.log(str.toUpperCase()); // 'HELLO WORLD'

Practical Example

function shout(message: string) {
  return message.toUpperCase() + '!';
}
console.log(shout('hello')); // 'HELLO!'

Advanced Usage

const code = 'abc123';
console.log(code.toUpperCase()); // 'ABC123'

Understanding String.prototype.toUpperCase

The String.prototype.toUpperCase method in JavaScript returns the calling string value converted to uppercase. It belongs to the String object and is one of the most widely used methods for working with string values in modern JavaScript and TypeScript applications.

The method signature is string.toUpperCase(). When called, it returns a new string with all characters converted to uppercase. Understanding when and how to use toUpperCase() helps you write more expressive, readable code.

Common use cases for String.prototype.toUpperCase include data transformation, input validation, API response processing, and building reusable utility functions. It works well alongside related methods like string-tolowercase, string-localecompare, enabling you to chain operations together for complex data manipulation pipelines.

Browser support for String.prototype.toUpperCase is excellent across all modern browsers including Chrome, Firefox, Safari, and Edge. It is also fully supported in Node.js and Deno. For older environments, transpilation with Babel or a polyfill may be needed.