<!DOCTYPE html> <html> <body> <h1>Element 对象</h1> <h2>children.length 属性</h2> <p>"myDIV" 有多少子元素?</p> <p id="demo"></p> <div id="myDIV"> <p>我是段落。</p> <p>我是段落。</p> <p>我是段落。</p> </div> <script> let count = document.getElementById("myDIV").children.length; document.getElementById("demo").innerHTML = count; </script> </body> </html>