<select id="param1">
<option>學號</option>
<option>姓名</option>
<option>年齡</option>
</seclect>
<script>
window.onload = funciton(){
var param = document.getElementById("param1");
param.onchange = getParam(){
var text = param.value;
}
}
</script>

<select id="param1">
<option>學號</option>
<option>姓名</option>
<option>年齡</option>
</seclect>
<script>
window.onload = funciton(){
var param = document.getElementById("param1");
param.onchange = getParam(){
var selectIndex = param.selectIndex; //獲得被選項的引索號
var text = param.options[selectIndex].text;
</script>