form.on('submit(formDemo)', function (data) {
 var fd = new FormData($('form')[0]);
 $.ajax({
 type: "POST",
 url: '/admin/adduser.do',
 data: fd,
 async: false,
 cache: false,
 contentType: false,
 processData: false,
 success: function (res) {
 if (res.status == 200) {
 layer.msg(res.msg, {time: 2000});
 var url = "/admin/views/users.html"; // 跳轉
 setTimeout(function () {
 window.location.href = url
 },2000);
 } else {
 layer.msg(res.msg, {time: 2000});
 }
 }
 });
 return false; // 這段很關鍵
 });

<script src="../assets/layui.all.js"></script>
<script src="../assets/layui.all.js" charset="utf-8"></script>
<script src="../jquery.js"></script>