String.prototype.toUpperCase()

Baseline

20157

toUpperCase() String

const sentence = "The quick brown fox jumps over the lazy dog.";

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

toUpperCase()

toUpperCase() JavaScript

console.log("alphabet".toUpperCase()); // 'ALPHABET'

`this`

this

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

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

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


ECMAScript 2027 LanguageSpecification # sec-string.prototype.touppercase

String.prototype.toLocaleLowerCase()
String.prototype.toLocaleUpperCase()
String.prototype.toLowerCase()

MDN

MDN 2025822

GitHub

String
1. String()
1. length
Object/Function
1. __proto__
2. constructor