# 用JS判斷下拉框是否選中 ~~~ <title>Js判斷下拉框</title> <script> function ss(){ var slt=document.getElementById("aa"); if(slt.value==""){ alert("請選擇一個項目"); return false; } return true; } </script> <form method=post onsubmit=" return ss()"> <select id="aa"> <option value="">請選擇</option> <option value="1s">一</option> <option value="2u">二</option> </select> <input type=submit value="提交"> </form> ~~~