<!DOCTYPE html> <html> <body> <h1>Element 对象</h1> <h2>innerHTML 属性</h2> <button onclick="myFunction()">试一试</button> <p id="demo">单击按钮将此文本加倍。</p> <script> function myFunction() { const element = document.getElementById("demo"); element.innerHTML += element.innerHTML; } </script> </body> </html>