【JavaScript】填坑，表单提交不执行Ajax方法

一开始我是这么写的

 1 <form id="form0" class="ui large form" action="" method="">
 2                 <div class="ui segment">
 3                     <div class="field">
 4                         <div class="ui left icon input">
 5                             <i class="user secret icon">i>
 6                             <input type="text" name="nickName" placeholder="昵称">
 7                         div>
 8                     div>
 9                     <div class="field">
10                         <div class="ui left icon input">
11                             <i class="user icon">i>
12                             <input type="text" name="username" placeholder="用户名">
13                         div>
14                     div>
15                     <div class="field">
16                         <div class="ui left icon input">
17                             <i class="lock icon">i>
18                             <input type="password" name="password" placeholder="密码">
19                         div>
20                     div>
21                     <div class="field">
22                         <div class="ui left icon input">
23                             <i class="lock icon">i>
24                             <input type="password" name="rePassword" placeholder="再次输入密码">
25                         div>
26                     div>
27                     <div class="field">
28                         <div class="ui left icon input">
29                             <i class="lock icon">i>
30                             <input type="email" name="email" placeholder="邮箱">
31                         div>
32                     div>
33                 div>
34                 <div class="ui error message">div>
35                   <button type="button" id="SignUser_btn" class="ui fluid large teal button m-margin-button-mini" >注册button>
36                   <button type="button" id="back_btn" class="ui fluid large teal button" onclick="backHome()">返回button>
37             form>

点击注册以后

1.  var formData = $('#form0').serialize();
2.  alert(formData)

这两句也能被执行，搞了好久才发现，不能把按钮写到form表单，不能把按钮写到form表单，不能把按钮写到form表单