function judge(id,pwd){    if(id.value==null)    {        document.getElementById("tip").innerHTML="請輸入賬號";    }    else    {        document.getElementById("tip").innerHTML="請輸入密碼";    }}以上是函數(shù)部分。Q1:<form action="" method="post" name="register">    <input type="text" id="id" placeholder="請輸入賬號" class="form-control" style="margin-bottom: 5%;">     <input type="password" id="pwd" placeholder="請輸入密碼" class="form-control" style="margin-top: 5%; margin-bottom: 3%;">    <span class="tip" id="tip"></span>    <input type="submit" value="登錄" class="button" onsubmit="judge(document.getElementById('id'),document.getElementById('pwd'))"></form>為什么不能實現(xiàn)元素處出現(xiàn)"請輸入賬號"的效果？Q2：<form action="" method="post" name="register">    <input type="text" id="id" placeholder="請輸入賬號" class="form-control" style="margin-bottom: 5%;">     <input type="password" id="pwd" placeholder="請輸入密碼" class="form-control" style="margin-top: 5%; margin-bottom: 3%;">    <span class="tip" id="tip"></span>        <!--以下為修改代碼-->    <button class="button" onclick="judge(document.getElementById('id'),document.getElementById('pwd'))">登錄</button></form>這樣能實現(xiàn)效果，但是頁面會重新加載，效果一閃而過。為什么？如何調(diào)整？Q3:<form action="" method="post" name="register">    <input type="text" id="id" placeholder="請輸入賬號" class="form-control" style="margin-bottom: 5%;">     <input type="password" id="pwd" placeholder="請輸入密碼" class="form-control" style="margin-top: 5%; margin-bottom: 3%;">    <span class="tip" id="tip"></span>        <!--以下為修改代碼-->    <button class="button" onclick="judge(id,pwd)">登錄</button></form>為什么效果同2？id名也能引用一個對象？Q4:<form action="" method="post" name="register">        <!--將id改為name-->    <input type="text" name="id" placeholder="請輸入賬號" class="form-control" style="margin-bottom: 5%;">     <input type="password" name="pwd" placeholder="請輸入密碼" class="form-control" style="margin-top: 5%; margin-bottom: 3%;">    <span class="tip" id="tip"></span>    <button class="button" onclick="judge(id,pwd)">登錄</button></form>為什么效果同上？難道name也能引用一個對象？