帮忙看下...很基础JS问题..谢了

我这里可以的啊，只不过要把换个位置
<body>
    <form>
        <select id="Year">
            <option>ONE</option>
            <option>TWO</option>
        </select>
        <select id="Month"></select>
        <select id="Day"></select>
    </form>
<script language="javascript">
    var objYear = document.getElementById("Year");
    var objMonth = document.getElementById("Month");
    var objDay = document.getElementById("Day");
    objYear.onchange = function()
    {
        alert("!!");
    }
</script>
</body>

解决方案 »

  1.   

    同意楼上的,建立监听的时候应确保你的监听对象已经建立
    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <script language="javascript">
            window.onload=function(){
             var objYear = document.getElementById("Year");
             var objMonth = document.getElementById("Month");
             var objDay = document.getElementById("Day");
                objYear.onchange = function(){
    alert("!!");
    }
            }
        </script>
    </head>
    <body>
        <form>
            <select id="Year">
                <option>ONE</option>
                <option>TWO</option>
            </select>
            <select id="Month"></select>
            <select id="Day"></select>
        </form>
    </body>
    </html>