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<!DOCTYPE html> <html> <body> <form> <select id="mySelect" size="4"> <option>苹果</option> <option>桔子</option> <option>凤梨</option> <option>香蕉</option> </select> </form> <p>单击该按钮可显示下拉列表中的选项数。</p> <button onclick="myFunction()">试一试</button> <p id="demo"></p> <script> function myFunction() { var x = document.getElementById("mySelect").options.length; document.getElementById("demo").innerHTML = "已在列表中找到 " + x + " 个选项。"; } </script> </body> </html>