<!DOCTYPE html> <html> <body> <h1>JavaScript 字符串</h1> <h2>toUpperCase() 方法</h2> <p>toUpperCase() 将字符串转换为大写字母:</p> <p id="demo"></p> <script> let text = "Hello World!"; let result = text.toUpperCase(); document.getElementById("demo").innerHTML = result; </script> </body> </html>