验证用户名，密码，验证码，发送alax请求进行登录代码

//html代码    
<div class="layui-form" id="larry_form">
             <div class="layui-form-item">
                   <label class="layui-form-label">用户名:</label>
                   <input type="text" name="userName" required  lay-verify="" autocomplete="off" class="layui-input larry-input userName" placeholder="请输入您的用户名">
             </div>
             <div class="layui-form-item" id="password">
                   <label class="layui-form-label">密码:</label>
                   <input type="password" name="password" required lay-verify="password" autocomplete="off" class="layui-input larry-input psw" placeholder="请输入您的登录密码">
             </div>
             <div class="layui-form-item larry-verfiy-code" id="larry_code">
                    <input type="text" id="code" name="code" lay-verify="" autocomplete="off" maxlength="4" class="layui-input larry-input " placeholder="输入验证码" >
                    <div class="code">
                           <div class="arrow" style="opacity:0.6;filter:alpha(opacity=60);"></div>
                           <div class="code-img"><img src="/randomCode" alt="" class="layui-disabled" style="opacity:0.6;filter:alpha(opacity=60);" id="codeimage" disabled="disabled"></div>
                           <a id="change" class="change" style="opacity:0.6;filter:alpha(opacity=60);" title="看不清,点击更换验证码"><i></i></a>
                    </div>
             </div>
            
             <div class="layui-form-item">
                  <button class="layui-btn larry-btn submit" lay-filter="submit" lay-submit>立即登录</button>
             </div>
        </div>

    $(document).keydown(function(event){
        if(event.keyCode==13){
            $(".submit").click();
        }
    });
    $('.submit').click(function(){
       var userName = $('.userName').val();
        var psw = $('.psw').val();
        var code = $('#code').val();
        if(userName.trim()==''){
            layer.alert("用户名不能为空！", {icon: 2,title:'提示'});
            return;
        }
        if(psw.trim()==''){
            layer.alert("密码不能为空！", {icon: 2,title:'提示'});
            return;
        }
        // if(code.trim()==''){
        //     layer.alert("验证码不能为空！", {icon: 2,title:'提示'});
        //     return;
        // }
       $.ajax({
           type: "post",
           url: "/login",
           // data: "userName="+userName+"&password="+psw+"&code="+code,
           data: "userName="+userName+"&password="+psw,
           success: function (data) {
               var message = data.msg;
               if(data.code === '0'){
                   layer.msg(message, {icon: 1, time: 1000});
                   setTimeout(function () {
                       window.location.href = 'index.html';
                    }, 1000);
               } else {
                   layer.alert(message, {
                       icon: 2,title:'提示'
                   });
                   // $('.userName').val('');
                   // $('.psw').val('');
                   // $('#code').val('');
                   // // $("#codeimage").attr("src", '/randomCode?t=' + Math.random());
                   return;
               }
           },
           error: function () {
           }
       })
    })