$.ajax post data error,stay in curren page

//form 
//ajax提交表单 不需要依靠form标签。
//我出现的问题是，在有<form action="/login" method="post">....</form>的时候，
//ajax error处理函数，会自动跳转到一个页面，页面中显示返回的结果 例如{msg:'error'}
 16 <div class="login">
 17     <p>
 18         <label for="login">用户名:</label>
 19         <input type="text" name="userName" id="userName" placeholder='' value="example">
 20     </p>
 21 
 22     <p>
 23         <label for="password">密码:</label>
 24         <input type="password" name="password" id="password" placeholder='' value="example">
 25     </p>
 26 
 27     <p class="login-submit">
 28         <button class="login-button">Login</button>
 29     </p>
 30     <p class="forgot-password">请输入用户名和密码</p>
 31     <!--p class="forgot-password"><a href="index.html">Forgot your password?</a></p-->
 32 </div>
 
 
 //ajax
 34 <script>
 35     $(document).ready(function(){
 36         $('.login-button').on('click',function(){
 37             var userName = $('#userName').val();
 38             var password = $('#password').val();
 39             console.log(userName,password);
 40             if(!userName.length){
 41                 alert('请输入用户名！');
 42                 $('#userName').focus();
 43                 return false;
 44             }
 45             if(!password.length){
 46                 alert('请输入用户名！');
 47                 $('#password').focus();
 48                 return false;
 49             }
 50 
 51             $.ajax({
 52                 url:'/login',
 53                 type:'post',
 54                 data:{userName:userName,password:password},
 55                 dataType:'json',
 56                 async:true,
 57                 success:function( result ){
 58                     console.log('success',result);
 59                     window.location.href='/home';
 62                 },
 63                 error:function(err){
 64                     console.log(err);
 65                     $('.forgot-password')[0].innerHTML = '您输入的账号或密码有误，请重新输入';
 66                 }
 67             });
 68         });
 69     });
 70 </script>
 
 
 
 
 //backend
 11 exports.login_check = function(req, res){
 12     var userName = req.body.userName;
 13     var password = req.body.password;
 14     console.log('================',userName,password);
 15     if(userName=='example' && password=='example'){
 16         login = true;
 17         req.session.userName = userName;
 18         res.send(200,{msg:'ok'}); 
 19     }else{
 20         res.send(400,{msg:'error'});                                                                                                                                           
 21     }
 22 };