為什么按了更改外觀的按鈕，"p2元素class的值為”不會變成two？怎樣才能達(dá)到效果？
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>className屬性</title>
<style>
? ? body{ font-size:16px;}
? ? .one{
border:1px solid #eee;
width:230px;
height:50px;
background:#ccc;
color:red;
? ? }
.two{
border:1px solid #ccc;
width:230px;
height:50px;
background:#9CF;
color:blue;
}
</style>
</head>
<body>
? ? <p id="p1" > JavaScript使網(wǎng)頁顯示動態(tài)效果并實現(xiàn)與用戶交互功能。</p>
? ? <input type="button" value="添加樣式" onclick="add()"/>
<p id="p2" class="one">JavaScript使網(wǎng)頁顯示動態(tài)效果并實現(xiàn)與用戶交互功能。</p>
? ? <input type="button" value="更改外觀" onclick="modify()"/>
<script type="text/javascript">
? function add(){
? ? ? ?var p1 = document.getElementById("p1");
? ? ? ?p1.className="one"; ?
? }
?function modify(){
? ? ? ?var ?p2 = document.getElementById("p2");
? ? ? ? ? ? p2.className="two";
? ? ? ? ?}
? ? ? document.write("p2元素class的值為；"+ p2.className);
? ? ? ?
</script>
</body>
</html>
2015-11-16
<script?type="text/javascript"> ???var?i=0; ???function?add(){ ??????var?p1?=?document.getElementById("p1"); ??????p1.className="one"; ???} ???function?modify(){ ??????var?p2?=?document.getElementById("p2"); ???????????i++; ????????if(i%2==0) ???{ p2.className="one";} ????????else ???{ ??????????p2.className="two"; ???} ?? ???} </script>2015-11-16
<script?type="text/javascript"> ???????var?i=0; ???????function?add(){ ??????????var?p1?=?document.getElementById("p1"); ??????????p1.className="one"; ???????} ???????function?modify(){ ??????????var?p2?=?document.getElementById("p2"); ???????????i++; ????????if(i%2==0) ???????????{ ????????p2.className="one";} ????????else ???????????{ ??????????p2.className="two"; ???????????}?????? ???????} ????</script>2015-09-19
document.write("p2元素class的值為；"+ p2.className); ?把這句話在modify中再寫一遍