目前，當字段為空且無效時，該字段將變為紅色并顯示描述文本。但是，當用戶正確填寫字段時，如何使字段和文本消失呢？HTML 中的代碼：<label for="email"><b>Email</b></label>        <label id="lblemail" style="color: red; visibility: hidden; float: right;">Invalid email</label><br>        <input type="text" placeholder="Enter Email" name="email" id="email"><br>JS 代碼：var email = document.getElementById("email");if (email.value.trim() == "") {    email.style.border = "solid 1px red"    document.getElementById("lblemail").style.visibility="visible";    return false;} else {  return true; }