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<!DOCTYPE html> <html> <body> <h3>如何访问 SELECT 元素的演示</h3> <select id="mySelect" size="4"> <option>苹果</option> <option>Pear</option> <option>香蕉</option> <option>橙子</option> </select> <p>单击该按钮以获取在下拉列表中找到的选项元素的数量。</p> <button onclick="myFunction()">试一试</button> <p id="demo"></p> <script> function myFunction() { var x = document.getElementById("mySelect").length; document.getElementById("demo").innerHTML = x; } </script> </body> </html>