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<!DOCTYPE html> <html> <style> .example { color: red; width: 150px; font-size: 20px; } </style> <body> <h1>HTML DOM Attributes</h1> <h2>length() 属性</h2> <button id="myButton" onclick="myFunction()" class="example">试一试</button> <p>上面的按钮有多少属性？</p> <p id="demo"></p> <script> let num = document.getElementById("myButton").attributes.length; document.getElementById("demo").innerHTML = num; function myFunction() {} </script> </body> </html>